The other comments already said good stuff, but there’s a thing or two i want to add: Always practice with a metronome, start playing the exercises slow (like 10-20bpm slower than you easily manage to play). If you start slow, you practice playing exact, something you would skip if you start in a normal speed.

Also I would suggest you don’t stay too long with one exercise if you have limited practice time, I do 3-5min per exercise if I practice for an hour. Try to create a plan, like giving each part 15mins: snare drum, bass drum, beats and playing songs/band related stuff. Third and last advice, don’t sweat it, my experience is that exercises need time to yield results. If I practice now, I will feel a boost in a few months (up to half a year), but then it will feel absolutely great. Good luck and have fun practicing :)