Second hand can be a minefield if you are new and don't really know what you are buying. sure you can get some great second user kit bargains, but not everything can be as good as it seems, people are often selling their mistakes. I suggest going into one of your local clubs and see what they run and speak to a few people. They most certainly will run 2wd buggies, so that's a really good cheap starting point. Whilst you can get cheap rtr 4wd cars, they will quickly become money pits, and you might be best off with a higher quality 4wd kit, if that's what you want to run. You will need to double your budget for 4wd, being realistic.
I'd recommend two options for rtr 2wd:
http://www.rccarshop.co.uk/index.php...-red-5385.html
Team Durango DEX210 rtr. comes with a great starter package of sensored motor/esc. will run great out of the box. You just need to add on a charger and battery(s) to get running. That will run a bit more than £300, more like £350-370 if you select 1/2 decent starter gear that will last you. This will upgrade with addons and hopups and you can convert to mid motor when you wish.
The other option is the team associated B4.1 RTR:
http://www.rccarshop.co.uk/index.php...brushless.html
Quite a bit cheaper for the kit, still needs charger and battery, but you will get this well under your budget. I think the steering servo needs replacing for a faster one as the first upgrade, and the ESC/Motor combo is sensorless, so not the best, but fine for starters. spares are cheap, every meeting will have someone with a B4, so someone always has some spares should you need anything. it can be upgraded as you need to full world championship winning spec, and mid motor options.
Both of those will give you great starter cars with the potential to grow as you learn and practice. I wouldn't look at any others options, it's just not worth it, as you will be throwing good money after bad on something that won't run as well as those.
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Good luck and welcome to oople!