Make sure you have a heat proof dish or three that will fit inside the IP. It needs to be <8" at the widest, so for square dishes that's the diagonal. I don't think Pyrex is safe if you want to broil, so you may need a metal dish or ceramic ramekins/souffle dishes.

A collapsible veggie steamer basket works better for catching smaller food than the wire trays. People recommend the OXO one, but I like my cheapo one.

If you plan to even attempt yogurt or desserts you will need an extra sealing ring. My first IP meal was ham & bean soup, and my gasket still smells like ham two months and several meals later.

I have an extra inner pot and I really like being able to cook while one pot is in the fridge or dishwasher.

I make soup in my rice cooker! Just toss in the ingredients and wait for it to bubble. Give it a stir every now and then to make sure nothing's stuck to the bottom.

For steaming stuff you can get a collapsible steaming basket that fits inside the pot (like so: https://www.amazon.com/dp/B0029728H0/ref=cm_sw_r_cp_apa_i_NK6jDbQ8ZF9JN), or rig one with a steamer stand and a cake pan (or aluminium tray/pan with holes punched in).

As an example I have used my rice cooker to steam potatoes to make mashed potatoes! :)