Great reply by Kitaru,
Im currently a lvl 39 (balance spec) and im loving the class, it is so diverse and engaging, I haven't even thought about anything other than what comes next. I know a couple people who became "bored" with their jedi guardians because of the melee only aspect and swtiched to shadow consulars and love the diversity it offers.
I would recomend to stay on 1 planet till all side quests etc are done, and if possible doing all 2 & 4+ Heroics, aswell as each flashpoint as the gear rewards from killings bosses and completion of the instances give great gear.
Also remember to ask others in groups if they done need the gear and you companion would benefit from it to atleast ask.. whilst it may seem cheeky, if your going to get some use from it, it can also help your companions alot. Just bare in mind that others may also require gear for companions etc so be sure to come to some agreement before hand.
I must admit I find it tricky gearing companions also, but that is a personal choice as Ive chosen to spend money leveling my Treasure hunting/Artifice/archaeology. but in tern it does reward you with lockboxes which can give you decent gear for all classes to either use/sell. also working together as a guild is vital. as our guild helps eachother out massively by giving any unwanted lower level gear to those who are either lower leveled or not able to play as much.