This depends on your budget and requirements, but an original Mini is always an excellent purchase for first-time classic car projects. There's lots around, it's very easy to work on, parts aren't expensive and it'll fit in even the smallest of garages. It's also very good fun to drive. If you need something a bit bigger then cars like the VW Beetle are a good purchase, or an MGB as a classic sports car - again, these are plentiful and parts are everywhere. If you want something newer or sportier, early Mazda MX-5s or Toyota MR2s are great project cars - just watch for severe corrosion.