Is that dollars or pounds?
How about going the miniature root? 4ml to 10ml sizes can be had in diddy versions of the full sized bottles for under your budget and if you're already rotating a few colognes, should last long enough to let you know if you want a full bottle. The Burberry's and Bvlgari's seem to come up a lot, and both have something in their lines you should like. Plus, if you want to trade to a big bottle, you can usually find them at a good price somewhere.
Well, you did say start small ;)