I suppose it depends on what trails who go on really. Yes i agree it would be better to get 'the feel' for the bike first though, before heading out on a track, especially as youve never been on one before. Just make sure you go on some 'easy' routes to start with as ive been riding off road and racing for around 10 years and i still struggle on most routes we go on lately. Some are ridiculous! As jacko said it will teach you more about bike control than any track tuition would. You really need to know and understand what the bike can do before pushing it on track.

Id personally just get a bike and all the gear and go for it (if your in a position to do that of course). Ive never come across someone who has tried it and then decided NOT to persue it again.