Going to echo everyone else here really:
-Budget as much as you can and get as newer model as you can, and try and ensure you can trace its history, maintenance, hours run etc
-4T (with Elec Start if avail), 2T are a constant maintenance item, more on off on the throttle, narrower useable power (read you gotta be on it to win it!!!), massively reduced times between rebuilds etc
-Enduro spec bikes will offer slightly longer gearing, heavier fly wheel, different suspension options and generally be a little more friendly on the heart and wrists initially, but will still offer extreme hi-adrenaline moments and can certainly tackle the whoops and table tops when your ready, but also offer the option for an MoT etc for green lane-ing if that's your thing.
-Moto-X spec bikes are more focused and will usually have firmer (not road spec hard mind) and longer travel suspension, smaller fuel tank and slightly different hubs/rotors/wheels to enduro spec, but most are completely interchangeable.
-Brand? Well this is completely a personal choice and a costing exercise in most cases... KTM and Husky come from the same factory and could be considered similar to buying a Audi vs a VW vs a SEAT, the models in their ranges can be a confusing myriad of numbers and letters that usually don't allude directly to a cc so homework needed there! from Japan my personal choice is Yam - a sorted YZF would be my go to, the newer Suzi RM is a rebadged Kawa KX or vis versa and the Honda CRF is a nice piece of kit (like KTM though they've started adding letters etc that are different specs from just enduro or Moto-X, so check carefully), they all ride subtly different and if you could get out with your mates and try different options before you buy would be my advise.
-Size - 250 all the way to start, a 450 will put you off ever wanting to go off-road ever again, they are a handful (understatement of the year), heavier (and this matters so much more than on a road bike) and solely focused on causing your early demise unless you are ryan vullopoto!:biggrin-new:
-Before any of this make sure you get some good riding kit, this is a must! Ankle support/protection (they take a pounding) through good boots and chest/back protection (a roosted rock to the chest even through armour can leave a nasty bruise and make breathing interesting! and when she flips you over the bars after a miss timed whoop section you'll be glad of the same protection to your spine!!) is really important, followed by knee/shin guards and then possibly a neck brace, decent goggles and the helmets as with the road is a budget/fit/comfort thing and can be had fairly cheap to mega bucks!
-finally, consider how you will transport it, and have a travelling tool kit and spares, fuel etc loaded and ready to go (think track day stylee if you have experience with those), and fluids/energy intake for you!!
-oh and try not to tank it full of ale the night before! this activity will have you in knots in mins if hungover or a little out of shape!!
Here endeth the sermon, now get out there and enjoy the dirt...lol
:dirtbike_smilie: