Hi and welcome
First thing to do is read up on purchasing rules.
You'll have to ask one of your parents to buy it and it will have to be painted a bright colour ('TwoTone', usual choice is Red, Blue, Green)
Also look at Jing Gong (JG), CYMA and Specna Arms for good & well priced gunz.
If you intend to use it for actual skirmish games then you should also look into getting a couple of LiPo batteries and a decent charger.
Search the forum for 'lipo battery' and 'intelligent charger'.