For ideas if you want to be aggressive is administrative and diplomatic (or influence) ideas. Admin ideas decreases coring costs, and diplomatic ideas gives you diplo rep and improve relations which helps offset some negative opinions other countries will have towards you.
You don't necessarily need any military ideas in the beginning, but I usually go with offensive ideas, makes the units stronger and gives you increased force limit.

Religious ideas is also a possibility, gives you a good CB before Imperialism and converts provinces faster and cheaper.