As a SAM all you have to do is know what potential level 2 and 3(in the 66ish levels) Skillchains you can do vs the mobs. You do have to research the mobs element so you can try to do a skillchain that is not the same element as the monster and hopefully with the monster's weakness. You also would like to try to see which melee you are pairing up with. If your friend is a DRK you should try to find out potential skillchains you and your friend can do if you both decide to party with one another. Same with every other job you party with, find the best potential skillchain, with the two partners you skillchain with, vs the type of monster.

DRGs are mainly damage dealers with their subjob being very complex outside of exp parties(will leave it out unless you want a long talk about it). Their power excels from level 1-66 where other DDs get their powerful WSs then. Even post 66 their damage over time with the wyvern out will be greater than most if not all other damage dealers if equipped right. Dragoons work well with THFs and /THFs post 60, they are great skillchain openers because their WS dont hit as high a dmg as other DD as you go up the levels(they are in no means weak however), so their power in opening Distortion and Light SKillchains is what makes them good. They are masters of those two SCs, and are good buddies when needed to lose hate. Their jumps if used right can easily make their TP raise dramatically. They gain TP faster than alot of jobs with the exception of SAM, and is on par with other fast TP gainers like WAR or MNK if they use Jumps right.

A DRG with good skill can keep up with a WAR with a kraken club and do two SC a fight. Your main advantage is faster TP gain if played correctly, bonus vs flying enemies, versitility in subjob(so level WHM THF and WAR up depending on the party) thats not limited to exp parties, highest damage over time, a little more accuracy than other 2h jobs(so up that STR!), and hate shedding tools along with easy openings for Distortion and Light Skillchains. The disadvantages are that without your wyvern you are weakened in almost every way(the wyvern and dragoon are one unit, and should be treated as such, your wyvern is indispensible) so watch for AoE, your WS as you get higher in levels are not as strong as other DDs(however your DoT remains top), their limited armor selection, their disadvantage vs skeletons without blunt lances and/or staves, bad HNM scene compared to some jobs, and long party wait times due to misconceptions of the job.