Which race are you…Human, Dwarf, Half-Orc...? It may give you experience penalties depending on your race and third class... Also, please tell us what feats you have taken so far…
Bard is a good class if you want to start slow with casting magic spells. You get Spellcraft, Tumble and Use Magic Devices as class skills. He would have a bard song and a limited choice of spells. Note that these are arcane spells subject to failure if you cast them while wearing armor.
Another choice would be a Cleric. He would get healing and buffing spells that he could cast in armor.
A rogue would get you lots of skills. As for spells, he could “fake it” with high ranks in UMD and a lot of scrolls.
I can suggest better when I get more information on your character.
