As a general rule, you gain very little from practising what you are already good at.
Similarly, practising something that's substantially beyond your technical capabilities can do more harm than good.
So the most productive areas to work on are those where you can sort of get through them okay but only at a slowish speed or you make a bunch of mistakes.
I've got quite a collection of various methods, but the most comprehensive and useful by far is Arban. Whether you're a raw beginner, or a seasoned professional soloist, just about everything you will ever need is there.
In each section there will be a bunch of stuff early on that you can play comfortably and cleanly at a metronome speed of MM 120. Skip these for now. Find the exercises which you struggle with at MM 100, in each section. These are the ones to work on and where you will maximise your rewards.
My own approach to a new exercise is as follows.
1) Set the metronome to MM=60 and practise the final bar until I hit every note cleanly, and with a really nice tone, treating it somewhat like a miniature flow study.
2) Repeat step 1) but for the final two bars.
3) ...and so on until you can play the full exercise faultlessly most times.
4) Repeat 1) to 3) for a few different dynamics and tongued/legato.
5) Repeat 1) to 4) for a few simple transpositions.
6) Repeat 1) to 5) at MM = 72, 84, 96, 108, 120
It's time consuming. Some exercises may eat up 20 minutes a day for a couple of months before you're reasonably happy with them. But properly done, the payback is immense. If you're working on several different sections at the same time (a good thing), you'll find that a small breakthrough in one section leads to further breakthroughs in others. And once one exercise is 'mastered', you'll probably find that the next bunch of exercises in that section come easily.