Your problem with not being able to get much height could be because you don't pre-load enough. I realised that i don't do that about a month a go and i've changed and i can go for things much bigger now. Riding with friends will be a great help though, it keeps you motivated and when you try to learn something and cant do it you can ask where you're going wrong and then you can sort it.
Your bike will affect your riding too, my bike was quite heavy when i got it and everything took so much more effort to do. I replaced the rear wheel and i could move that end of the bike around a lot easier after that so i would recommend making sure your bike is decent. Oh and the lack of engagements i had made things a lot harder too so i would recommend a decent freewheel/free hub.