There's a lot of things against you i.e finding an engine, fitting it, insurance, brakes and also a bit of a shite looking RS clio, unless you plan to colour code and get all sport bumpers etc which is even more expense.
I'm assuming this is your first car? I had a 1.2 and also thought about doing something like this, luckily I didn't and just had as much fun as I could with my mates driving around, eating fast food and chatting up the car slags, didn't crash and now at 18 years old i'm driving a GTi-6 for fairly reasonable insurance costs.
It's obviously your choice but we have all been in the same place once. Just try and get some no claims and start saving for a 172
It all sounds a bit condescending but I reckon its worth it in the long run