for my guild i started off with infantry then
infantry skill tree
impact,scattershot,refire and guided missile sentry+5
support skill tree
stockpile,barrage grenadier and supply drop +5
medic skill tree
fitness overload aid station and stat+5
and at level 69 you have one skill point and i put that into deploy and thats my build it makes it so you will rarely die you have inf ammo and grenades your turret can heal you along with helping you rip through all enemy types roland is by far the best for a beginner

in playthrough 2 the claptrap dlc scales to your level and gives you some pretty good weapons if you do it from the start of playthrough 2 i got a level 34 shotgun and level 34 assault rifle both of which took me to the end game never found a better weapon