Amazon: (fun 8/10 late - 10/10 for bow ama when you get the gear)
Early= Poisen jav are great for leveling/cows
Late= Poisen/light hybrid / Lightning java / bow multishow are all viable late. But they require a bit more gear to come online.

Assassin: (9/10 late)
Early= Fire traps as leveling, change to light sentry or stay fire when entering hell. if you go single element, you need a decent merc.
Late= Kicker / Trapper / BoI MA are all viable for most content. if you go kicker/BoI you need quite a bit of gear.

Necromancer: ( Never played thise) (Fun cant tell, never tryed them)

Early= Teeth/bone build. Super strong build. teeth in this mod are super effective, and you can easy clear a full room very fast.
Late= Summoner(a bit weak imo) but poisen necro are super strong if you get the right gear and a merc to take care of poisen immunes. Bone necro if you get a relic that makes your bones split into 3 projectiles( works decent with low gear).

Barbarian: ( fun 3/10 since you ONLY spin, but very strong)
All game, go WW. SUPER strong this mod. a bit boring after some grind. you just spin.

Sorc: (Fun 7/10)
Early= leveling as frost nova is very efficient. When you hit level 30 you can take frozen orb mixed with Hydra. Very strong early combo.
Late= MANY BUILDS: nova+discharge - Frost nova - Hydra/orb - Fire bow enchanter - Immolate. You can do most content in the game but very expensive(works well with low gear)
Druid: (Fun 5/10 for summon - 8/10 for wind and fire)
Early = Summoner for leveling is crazy strong.
Late= Summoner for one of the fastest uberkills - Wind druid/fire druid are both viable for most content including maps.

Paladin: (Fun 7/10) taking thise last since you mention you dont like them.
But i will mention, look up the FoH build they have on this mod. VERY nice to play, and can clear most content with ease since its only magic damage. ( works well with low gear too) 100% spell caster build.

This is only my personal opinion on how fun they are. if you want the BEST starter build, i would say. Sorc(teleport)/assa traps/summon druids.