Well. If you roll 3 good stats you can go for rogue 1/swashbuckler 3/rogue 2/swashbuckler x, taking daring outlaw for rogues sneak attack. This will help if you have high DEX and INT. You will have enough skills and much more fighting capability than rogue. If your cleric gets into the fight, you could replace the fighter role. Against undead and immune things you would be useless/ but you have the cleric for undead.
If you have time to study spells, tactics, etc off-game go for druid which is also core.Druid and cleric in the same party is overkill, but who cares.
If you don't then go for wizard- you still have to read your spells, but thats mostly when you level up. With wizard you can have supportive spells in your spellbook. You can also leave some slots open, and prepare extra spells when needed during the day.
You can also go for arcane trickster. Just be warned, its more a rogue with spells than a wizard with skills. The feat practiced spellcaster (if I recall correctly) will give you the caster levels you will be missing though, so spells like fireball will be useful for some time.
Rangers are also good support, but I don't know how to make one
I feel bard is hard to RP, and that he is weak when there aren't enough ppl in the party. But he still is support. But I would prefer a beguiler.
