Here’s my top tips for speedruns:

Make sure you get easy/speedrunable stages, stages with moving platforms or disappearing platforms can waste a lot of time.

Have shiftlock on, it makes it a lot easier to make wraparounds, and more.

If there’s a skip you think you can make, go for it. If it’s skipping whole levels, do it, even if it only saves a few milliseconds

Make sure you’re moving 24/7, if you aren’t moving, even for a short period of time, it can slow down your run a lot. So be wary of that, if you have to stop at any point to wait for something, then it’s reasonable

And my general look on things, don’t go for it instantly. Take your time as a beginner, and slowly but surely get faster over the days, weeks, even months or years. Going quick instantly will lead to a lot of mistakes and errors as you don’t have a better grasp on some of these levels and short cuts.

I hope this helps any beginners!!