Smooth,
Everyone has their favorite brands, but I have not heard anything bad about any of the current major brands (GasGas, Sherco, Scorpa, Montesa, Beta). If you plan to keep the bike awhile, you may be better off buying a bike that is a 1999 model or newer, as these models are a bit lighter and tighter. Trials bikes are suprisingly tuff in general and most are not stressed/worn like a typical used MX/Enduro bike. If you are of average adult weight, a 250cc or a 280cc provides plenty of power. Some claim a 175-200cc is all anyone would ever need to ride an event. I have been riding a 2002 GasGas 280 Edition (272cc) for almost two seasons and I am very happy with it.

I rode a vintage '78 Bultaco 350 before that. For an idea on prices see
http://www.gasgas.com/forsale.shtml or
http://www.trialsxchange.com/ or
http://www.umta.org/ or
http://www.nitrotrials.com/ . But if your budget says $1500 max, then you'll likely be looking at older models. Pre-'99 models will be a few pounds heavier. Pre-'94 models may be questionable as far as parts availability/condition. I have heard that the Yamaha TY250 monoshock (late '80's) can be a good starter bike if you have limited funds. You could place "Want Ads" on the sites I have listed above and see what comes your way. Maybe someone reading your post here has got an old bike looking for a new home.

Good luck... and see on the loop.
Dave
Dave