The easiest way to level a Kheldian, in my experience, is to embrace using Nova and Dwarf forms to their fullest. If we assume that you may deviate from that later on, then just stick with generic level 25 IOs - 6-slot the Nova & Dwarf base powers, (3 end mod, 3 tohit & 3 end mod, 3 dmg res, respectively), then add slots to any other power as needed. Those will act as your foundation, and should allow a pretty smooth journey to 50. After that, you can experiment with other builds using the other 2 builds you'll have then.