It may be worth starting off on something with an ISIS hub, but these are usually around the $300 or £200 mark unfortunately. :
you will most likely break something less by doing any sort of hopping, the club freestyle or a torker may keep you going enough to learn to ride though.
The size is up to you
6ft 3 here
I am about 200Lbs now and ride a trainer freestyle uni from UDC (had to replace pedals and cranks after bending them) and a KH29.
When I first started I was about 180lbs and rode a freestyle from ebay, cheap £30 job and bent it withing 3 days of getting it!
I would recommend getting something a little more expensive from UDC. If you are doing any type of trials you should be fine with any trials uni as they are built to take the pressure. Freestlye unis are a bit weaker so get yourself something a little more expensive!