Improved familiar is an excellent feat choice, imps are good as are earth elementals (earth glide for scouting) and air elementals. Improved initative is another good core feat. Beyond that I'd pick up spell focus in whatever school(s) with spells you know that have save DCs (conjuration in my case).
Not knowing what the rest of your party looks like makes it a bit difficult to pick spell but going in blind I'd choose:
1-silent image, charm person, grease, enlarge person, protection from evil
2-alter self, glitterdust, web, scorching ray*
3-haste, dispel magic (pick something else if another caster has this one), summon monster III*, stinking cloud*
*bonus spell via house rule
You have a flexible group of spells here and spells that target all three saves. You can do a little bit of everything so you're never in a situation where you're useless.