2 things to understand about Avid brakes
1. they come with the lever reach adjuster usually screwed all the way in - grab the appropriate allen key (good quality) and adjust the lever reach screw (its the piston rod), wind it out, don't worry about reach unless you have tiny hands as Avid's lever geometry is radically different to other brake manufacturers
a surprising thing about Juicy's is that once you wind the lever reach out, you get a substantial increase in piston effiency / power
2. Juicy 3 and some of the Juicy 5s come with "organic" pads, which feel very soft - the reason for this is that the 3 and some of the 5s were a cheaper brake aimed at more recreational users, and organic pads are marginally cheaper than sintered which helped make the brake more afffordable to OEM customers - if the brake has come from an OEM source to your retailer it may have organics fitted rather than sintered
swap the organics out for sinterered (metallic) and you will get a fierce brake!
3. any product mass-produced in 1000s of units will have quality control issues, and the cheaper the product, the lower the QC
probably half of the Juicy 3s I sold needed bleeding, less of the Juicy 5s needed bleeding and rarely any of the Juicy 7s needed bleeding
get them flushed / bled with DOT 5.1 (the Juicy 3 and older 5 / 7 usually has Dot 4) and with the sintered pads and lever reach you should have good brakes ;)
sorry i realised that's 3 things about Avid brakes, I can't count for sh*t but I can setup good brakes :)