A bit confused on the set/rep scheme as you have it listed. For example:
"2sets; reps 12,6,10,5,8,4; 30sec rest"
It notes 2 sets, but has 6 different rep schemes, so I can't tell exactly what you'd do for something like this. If it's just 2 sets for a major body part, what exactly are the reps you're doing for each set? Or, is this some sort of super-set concept? If you can clarify on that, it'll definitely help understand what you're doing better. That being said....
If you're just getting back to training after a longer layoff, hitting all major groups twice within a few days of each other is probably more than you need. Coming back to training after time off usually means you get more return for less time spent training vs. someone who has not taken a break in some time and is stuck at a plateau for progress. I'd consider something easier for the comeback that revolves around the main compound lifts that yield the best returns with more rest time. For example:
Day 1 - Leg training, throw in a few sets of ab work if you feel compelled, but it's not really necessary when just getting back to normal training again
Day 2 - rest
Day 3 - Upper back and chest training
Day 4 - rest
Day 5 - Lower back and shoulder work
Day 6 - rest
Repeat cycle after day 6, if needing more recovery time, add an extra rest day in on day 7.
For lifts, I'd suggest something more of the following -
Leg training -
- Squats done at least to parallel (preferably a few inches deeper), 2-3 warmup sets, then 5 sets of 8-10 reps (I normally like to suggest lower rep sets, but for getting back to regaining proper form after a break, better to go lighter with more reps than heavy with potentially bad form). Rest at least 2.5 minutes between sets, up to 4 minutes if necessary. It's not about sucking wind between and during your sets, it's about doing quality work for maximum results, and longer rest periods vs. shorter ones will make your sets more effective, you'll definitely have more energy to lift heavier. Remember, you say you want to put on weight, and making your lifting sessions into cardio-esque training with short rest periods will be contradictory to your goal.
- Glute/ham raises (if your gym has a glute/ham setup), 3x15 @ bodyweight (or, as many as you can manage per set, making sure to get at least 10 reps). If no glute/ham machine is available, do either leg curls seated or lying down, 3 sets of 10-12 reps or 1-legged Romanian deadlifts, 3 sets of 10-12 reps per leg
- Calf work is only needed if you have really small or underdeveloped calves. Unless that's the case, don't bother spending time on them. If you do them, just 2-3 sets will be plenty.
After proper deep squats done to near failure (or, maybe failure on the last set, but not on all sets) and some good hamstring work, most people should have little urge to do anything but crawl out of the gym if they give it 100%. Should you find that you have ANY energy left and want do do more, then thrown in some lighter leg presses, using only the bottom half of your foot to press the weight with legs shoulder width or slightly wider. 2-3 final sets of 15-20 reps and that should cure any feeling of needing to do more.
Upper back / chest training -
- Barbell or dumbbell rows, 2-3 warm up sets, then 4 sets @ 8-10 reps/set, rest 2-3 minutes between sets
- Close-grip (hands about 18" apart, close to torso width) flat barbell bench presses with no bounce off chest, 2-3 warm up sets, 3-4 working sets @ 8-10 reps/set, rest 2-3 minutes between sets
- Pull-ups (if you can do them), 4 sets of 8-10 reps, otherwise medium to wide grip pulldowns, same set/rep scheme
- Incline dumbbell bench press, 3 sets of 10-12 reps, 2-3 minutes rest between sets
- Barbell or dumbbell shrugs, 3-4 sets of 10-20 reps (I do better with higher reps, but everyone is different), no excessive "body english" to move the weight, if you can't shrug it without a bounce each time, it's too damned heavy for you, so drop the weight.
Forget adding in arm work, if you're doing the lifts here you won't need to do anything for triceps (torso width grip benching will take care of that part), and biceps will get plenty from the upper back work. Some of the guys I know with the biggest arms don't ever do any direct work, so if you hit the compound lifts hard and heavy, there's little to no need for most people to waste their time on arm stuff.
Lower back/shoulder training -
- Barbell deadlifts, 3-4 warm-up sets, then 5 sets of 8-10 reps to work on keeping proper form without going too heavy initially
- Standing barbell overhead press (use the power rack for this one, or, power clean the weight into position if you wish) - 2-3 warm-up sets, then 4 sets of 8-10 reps. Press to the front of the body, lower bar to clavicles on each rep (none of that "lower-to-the-ears-only" garbage here), start each rep from a dead stop on your collarbone. Use a hand position just with hands just outside shoulder width, where your thumbs would be close to touching your front delts at the start of each press.
- Lower back hyperextensions or lower back extension machine (either will be fine), 3 sets of 15-20 reps
- 1-arm dumbbell power clean (one power clean only) and press for each arm, 2-3 sets of 10-12 reps
After these sets, you will find your lower back, core, shoulders and triceps will be taken care of, another reason why there's little to no need for direct ab or arm work in this routine.
Not much more to say about this sort of plan other than that it leaves out the b.s., saves you time from spending a good portion of your sessions wasting it on direct ab/arm work, and gives plenty of bang for the buck. If you're short on time and your endurance is good, it's laid out in a way that on the chest/back and lower back/shoulder days, you can speed things up (if you feel compelled) by alternating the sets for each body part (such as, one set of pull-ups followed by a set of close-grip bench presses) and shortening rest periods down to 60-90 seconds. I don't recommend that at first, perhaps after a few weeks to get acclimated, but that's how I structure my own training, working non-conflicting body parts so I can occasionally shorten rest periods and keep things moving if I'm rushed. Just another option for a program of this sort.
Only other thing to mention is intensity, the most common lacking factor in a LOT of people's programs. Not every set needs to be to failure, rather, every set should be where you don't hold back anything, and give it your all. My sets usually go like this -
Say I'm doing barbell rows, 5 sets of 8 reps with the same weight, warm-up light sets are already over and done. My first working set, I'll get through the 8 reps pretty well, and feel like I might be good for 2-3 more if I fought with everything I had. 2nd set, I get through the 8 reps well enough, probably good for 1-2 more reps if I really fought for them. 3rd set, I get through the 8 reps, but know that one more at most is all I'd have been good for. 4th set, it's a bit of a fight to get that 8th rep in, an extra rep would be a 50/50 chance of completion at best if I'd tried it. 5th and final set, it's a killer to get that last rep in, no chance in hell of making another unless I rested about 10-20 seconds before giving it a try, nothing left in the tank to give to that lift at that point. For lifts with fewer sets (such as 3 sets total), just look at my notes for sets 1, 3 and 5 and that'll give a clear picture of how you should be feeling at that point. I mention intensity as most people gauge their true workout intensity moreso by what they THINK they are capable of giving vs. what they actually are capable of (usually based moreso on one's idea of not wanting to be "too uncomfortable" rather than going all-out and battling to make optimal progress), and many times, they sell themselves short. Basically, if you can converse with someone during your set or have any urge to do so for the first 20-30 seconds or so after your set is done, you're most likely not giving it your all, and proper focus and intensity should be a bigger concern.
It's a long reply, but that's what I'm known for
Keep it simple, use effective lifts done well with good form, eat plenty, get enough sleep, and good things will happen.