To master Celstial Magics you will first need to learn Read and Write and then Read Magic.

Now you can spend build on Spell Levels. You must have at least as many spells at the immediately lower level as you buy at a given level, and until you have at least four at the next lower level you must have MORE spells at that level.

Thus its valid to have; 2 level 1 spell slots and 1 level 2 slot. OR 3 level 1 and 1 or 2 level 2. But until you have 4 level 1 slots you can not just buy 4 level 2 slots. It ends up looking like a tower with a conical or pyramidal roof on top.

The list of Celestial Magic spells and their incants includes one pure damage attack spell at each level:

Each level also has a mix of protective, binding and utility spells.