Does 'for free' count in 'under 500 bucks'?
I'm not sure about your level of confidence on the neck and hopefully you are looking at electric rock guitar. But since you specified guitar technique, I presume you are looking beyond the basics. Anyhow, here are some books that I found useful...
Troy Stetina - Speed Mechanics for Lead Guitar
John Petrucci's Wild Stringdom
Guitar Gym - 20 part guitar course from Guitar Techniques magazine
Guthrie Govan - Creative Guitar
You could get these for free if you on a search for the above with a certain keyword at the end, if you know what I mean...
-- My current rig
Guitar: '98 MIJ Ibanez RG520 QS w EMG 81/60
Amp: Laney LC15R Tube, Fernandes 20W SS
Pedals: MI Audio Tube Zone Overdrive, Boss OD3, CS3, MT2, HM2, DS2, CE5, DD7, TU3, Beta Aivin DD2 Delay, Dunlop Crybaby 95Q, Stranger Vol Pedal, BBE SupaCharger
Others: Yamaha RBX 374 Bass, Yamaha MM-6 Synth, M-Audio Fast Track, Shure SM-57, Heet Sound E-Bow Plus
Wanted(pm if selling): EB VPJr/Boss FV500L,Ibanez w Original/Lo-Pro Edge