crossfit is a different animal .. i agree with the guys above me. natural supplements is what you should go after. juicing after 5 weeks isn't gonna give you a legup on guys you crossfit with who have been doing it a while. a big thing with crossfit is putting in the hours, those guys live it (atleast the ones who you probably look up to and want to beat) just like anything else.
also crossfit isn't bodybuilding.. if you want to build muscle its just not gonna work for you. crossfit is a combination of strength, endurance, and other things. crossfit guys are not bodybuilders at all. and bodybuilders aren't crossfit guys either. you want to build 'a little muscle' so crossfit is probably what you want to focus on so go out there and do it. 5 weeks and you already want to beat everyone? doesn't work like that.. it can take years to excell .. when i was an endurance athlete i would bust my ass everyday and put in the mileage, but i constantly was struggling to keep up with guys who had been doing it since they were 8. one of the guys broke his leg and couldn't even run for 6 months, he ended up coming back and 3 months later was running sub 20 minute 5K's again. from being on crutches to running 19 minute 5K's 3 months later.. why? cause he had built up years and years of memory through hours of training. so yes you gotta put in the hours, we aren't robots