NiallTrial

I'm 17 and have been riding bikes for ages and figured i would give trials a go. Somewhat strapped for cash, but have a WTP Bmx and another bike i could sell for some funds. I've got pretty good balance ect on a bike but need help on choosing my first trials bike. Wondering about peoples opinions on 20" vs 24". What makes are good for budget bikes? And how to go about learning the basics. Any links to bikes for sale would be appreciated. Thanks in advance.