I like the Nikon and Super Sniper. The Nikon maybe the best bet because in your price range you can get a nice variable low-mid power which give you some flexibility from up close shots to longer shots. Some have Bullet Drop reticles, plus Nikon has sharp glass.
http://www.swfa.com/c-10-nikon-riflescopes.aspx
The Super Sniper has good reviews, the only downside is a fixed 10x.
You definitely want to free-float the barrel. Either go with a smooth tube, or a tactical model with rails. Some brands that offer solid value for the money would by Yankee Hill Manufacturing, and Midwest Industries. Both companies have free float and non-free float rails so read the descriptions. Midwest Industries is easier to install. You remove the handguards, trim off the delta ring and springs then bolt the MI rails on. Easy 10-15 minute deal.
http://www.midwestindustriesinc.com/ind ... gory_id=68
Post any questions you have in the 68discussion page. The guys on this forum will jump in like crazy to answer your questions.