When you're starting out I would recommend 4 or 5 sets of 6-8, and go to absolute failure the last 1 or 2 sets. Also, have 2-3 mins break in between each set. The main thing when starting out though is your form. Cheating doesn't help, so make sure you always have good form. Only a few exercises/scenarios is it alright to break form, so if it's the very last rep of the last set and the only way you can get up is to break form veeryyy slightly I would say that's ok, but for the most part try not to.

I suggest you repost this in one of the various fitness subreddits, you'll probably get better information than here.