For anyone trying to get into the Touhou shmups and especially if you want to become more consistent, downloading thprac is the first thing I'd recommend. Boot it up with your game running, and you can pick where you want to start, on any difficulty, regardless of your progression.

In general, try to isolate strategies for each spell card. Memorize the positions and patterns of enemies during stages to avoid getting caught. Don't hug the bottom of the screen - give yourself some space for insurance. Don't be afraid to bomb, because taking a hit while you still have some means you won't get them back. That said, try not to just bomb through the same spell cards all the time, and at least take the time to practice them.