One of the easiest and cheapest ways I've found to get any kit ready for S/S is to throw on some neckwear in your favorite warm weather fabric. Unless you are really jonesin' for a wardrobe overhaul, all you need to do is pick up a few ties or bowties to get yourself ready for when that nice weather hits. If you rock a white oxford and chinos on the reg. you're pretty much 90% of the way there already. Tie on some madras, seersucker or gingham and your uniform is locked up for the next 6 months as far as I am concerned.
For the sartorial novice who isn't ready for some "go to hell" pants or shirting these kind of ties are a perfect introductory course in both fabric and color. Everyone from the lowest common denominators (i.e. J. Crew) to the exclusive gear hubs stock up on S/S neckwear so all you have to do is find a price point you can run with. Just remember to keep that tie width under 3" or under and you're set. Check out some options below (madras being my favorite of the bunch) complete with click through links because I work (blog?) hard for the money. Tie one on folks. Tie one on strong.