My accuracy was really low once too. This is what I did to fix it.
1. Play easier maps. For example, if you're regularly playing 4* stuff, try going down to 3.6, 3.4, 3.2* stuff. Keep going down until you can get good acc for
MOST maps near that star value.
2.Then you just work your way up. Sort your maps by difficulty, and just literally go up the list in song select and play every map you can and try to accuracy everything.
3. If you are getting bad accuracy on a map, don't bother playing it, skip it and move on to the next map (shouldn't bother if you get below 93% for sure, if you're getting around 94% then if the drop in accuracy is not caused by reading, i.e. you're mashing, then skip it. If it's caused by reading issues and not by mashing issues, then it's okay. If you're getting 95-98% then it should be fine to not skip it)
4. Eventually you'll have played all maps between x and x+y stars (for example, 3.5-3.8). You keep moving up until you start getting low accuracy on average for most of the maps near the star value at which you're playing - i.e. rememeber from #3 if yo
u get bad acc, you should skip it. This basically means if you're skipping songs a lot then you should go back down.
5. Start from the bottom back up, but skip any maps that you feel you can comfortably get 99%+ in, everything else you should play it again and try to get higher accuracy.
6. Work your way up doing the exact same thing as before, this time you should be able to climb higher than you did earlier, before going back and starting over.
This works best when you have a lot of beatmaps so consider getting the beatmap packs.
Eventually you'll be able to play harder maps with good acc.
One thing you should keep in mind is that this process will take place over a long period of time, so in your next session if you stopped at, say, ~3.6*, then rather than starting all over from the very bottom, just backtrack to 3.3-3.5* and work your way back up from there.
Also, avoid high bpm stuff until you can acc low/mid bpm stuff. You can easily take higher bpm stuff out of your search list by typing bpm<X where X = the bpm you don't want to go over.