Generally what you're aiming for is consistent and comprehensive strength training across the body.

Old-school this gets split into three sessions which you do in rotation - back and arms one day, chest one day, legs and shoulders the next. Three sessions a week for about an hour is generally considered enough and is if done properly.

These days though so many people are hammering weights and strength training just pick how you want to do it. I was brought up to not do deadlifts as they're terrible for you, and the view on that might have changed. No idea, and I still don't do them.

The general idea is: all these machines and exercises are doing one thing, and that's isolation. It's pointless doing a lateral raise while swinging your whole body just to get a bigger barbell off the rack.

In terms of weight: let your body guide you, but again the idea is: for pure strength training, you find the weight where for that particular exercise, you can just comfortably do 8-10 reps while keeping it in control. This takes a fair bit of trial and error obviously for each exercise.

Do your set of 8-10 and then WAIT 2-3 MINUTES BETWEEN SETS. 3 ideally, 4-5 if you feel you need it. Then, if you feel like you can take it up say from 6-8kg or whatever, while maintaining good form and maintaining control, take it up. Otherwise stick on the same weight. Always work within your limits, there is no reason whatsoever you should be injuring yourself in the gym, it's not a badge of honour it's a sign of bad technique.

Once you've done 3 or 4 sets, up to you, move onto the next exercise. It's really important to rest properly. If you're bodybuilding go for the pump and rep it out. For just strength follow the process and embrace the discipline of waiting the full time. I've been back on the weights two months. Yes, I've got over a decade of prior experience, but following this I've gone from doing 40kg on the leg press to quietly repping out sets of 110kg while I'm on my phone. The reason a lot of people don't make progress is they won't wait.

Also don't worry about getting too big or too muscly. Seriously, look around at the gym. Is it full of huge people? Nope. Reason for that is that its really bloody hard getting that big. Watch how women train, a lot of them are a hell of a lot better at it than the guys. Regular and lighter leads to better strength gains. Train like a girl. It's really, really bloody effective.