Been doing this for years. CJ Spiller should of been rostered. I would probably go over half to three quarters your budget. But it really depends how aggressive your league is, it will hurt to bid $72 and the next highest is $35. If its like my league most guys wont use their FAAB (free agent acquisition budget) correctly and will have a ton left for final couple weeks. Its more important to get most of the season out of an average player than 1-2 weeks out of someone that jumps in because of injury.
I am weak at WR in my league and bid about a quarter of my budget on Ogletree, Cobb, and Hill. Hoping to get all of them and see which one is legit.