Learn all the sounds you can starting with the basics of the btk’s first and keep practicing first. Don’t be that one guy who just spams throat bass everywhere cause if one of your friends do record you, you will cringe. And one more thing, if you’re asked to beatbox by your friends and you want to be technical although you just started… just beatbox a 5 second routine like B Hi S slightly faster:(Hi S Hi S) B S and if your sounds are clean that will impress them enough and so when practicing weird sounds like the liproll just practice it when you’re alone.
When you’re already 6 months in on beatboxing try to learn and master the tk’s and peh-k’s because that will help you become more complex of a beatboxer.
As for flow, don’t switch your tempos too much or too oddly.