Could i use permanent marker as a cheap substitute for nail varnish?

Yes, but know that it doesnt last long at all. In fact, it can wear off within minutes. Also, most permanent markers are the same price or slightly more expensive (like 5 cents) more than some nail polishes. Try NYC or something. If you have a WalMart or KMart close by, check out ALL of their shelves. Usually there's something below a dollar on one of the shelves. There are these itty bitty bottles called Bon Bons... kinda crap, but cheap! Again, look for NYC make-up products. The eyeliner and nail polish are the only really good products they have.