If I was you I'd upgrade the brakes first bud. Been in your position when I first had mine and quickly realised how poor the stoppers were even before up'ing the power. After that I'd put the parts on that don't require a remap first if you want to spread the cost so, plugs, air filter, intercooler, fuel pump and exhaust apart from the downpipe. Then when your ready for a map get the turbo and injectors fitted and then mapped afterwards.