As another comment said, use it gradually on what you want.

One of the most useful things are slots, warframe slots and weapon slots.

However don’t spend everything right away. You will keep the 1k plat, and you can also trade with other people if they have parts/mods you need (warframe.market) (don’t get scammed tho).

Dont spend it without actual need. Use it gradually for stuff you need like slots.