If you want to make a custom buggy go for it. I have seen some fantastic stuff made by people with little previous experience using what most people throw away. The thing you MUST do is plan exactly what you want to do before you start building. Once you start you can make changes if you need to but if you plan properly you wont heed to make many if any. Look around for 2nd hand stuff if you are like me (broke), you might even get some stuff for nothing from people that have parts they dont want or cars they dont use. I was just given a 1/8 Kyosho Mp6 by a mate. It needed a fair bit of work and cost about $50 in parts but it is now like new (except for a tired engine) it might be old but it is a ton of fun and it even beats some later stuff at out club.
Terry