Increase your effective Caster Level

Orange Ioun Stone: +1 Caster Level
Create Magic Tattoo (Spell, Spell Compendium): +1 Caster level
Ring of arcane might : +2
Prayer bead: +1
Practiced Spell Caster +4 caster level
Spell Penetration: +2 Caster Level (caster level checks only)
Spell Penetration, Greater: [stacks with spell penetration]

Note, that it would be silly for each f you not to take 5 levels of this class as part of your 5e to 3.5e respec since I said you can start another class at 5th.

I need a little more time to settle on a character sheet.

I did not see any community sheets for 3.5 so I was looking at either the core 3.5 sheet or the pathfinder sheet.

Pathfinder sheet: https://app.roll20.net/forum/post/4735667/pf-pathfinder-sheet-thread-6