This game was basically made to speedrun, so here are some tips:

4 directions are overrated. If you go diagonally, Cube will go slightly faster so you can speed things up.

Make use of the dev's kindness. The hitboxes are forgiving, so you can skim along the outer edge of a spike ball.

Find a pattern or safe spot for bosses. This is just in general to have ease with bosses.

Learn the layouts. To speed through the game and get your record just practice.