Bay of Plenty region is a lovely area, though the main tourist interest is in Geothermal Parks and 'the Māori cultural experience' - abd both of these centre round Rotorua. There's a full round-up of things to do at https://www.rotoruanz.com/things-to-do - and if you scroll down you'll see my thoughts on how to make your choice.
What's to do in Rotorua? Well, there's the wonderful lake, the German bathhouse and the lovely garden - which would be quite enough in most towns - but here there are also the two attractions of geothermal activity everywhere (Rotorua stinks of Hydrogen Sulphide) and 'the Māori cultural experience'.
Local Māori do a good job presenting the 'experience', but the people-intensive attractions are mainly available in the evenings - after all, during the day they do ordinary jobs and go to ordinary schools. These things come at a tourist price and they can be tiring - and belt-straining - so it's worth considering what's right for you. And unfortunately it's all wildly popular, so it gets booked out early.
Options as I'm writing this appear to be:
Free (1 hour): Visit Kuirau Park in the middle of Rotorua. A must-do 'first taste' of the geothermal stuff - but no Māori part.
$40 Whakarewarewa Geothermal Park (2 hours, any time): Just the Geothermal park, including the geysir and some of the more famous features, but not the more private bits of the park and no Māori part.
$45 Hells Gate (2 hours, any time): Geothermal, mud bath, spa etc. Self-guided, very good, and 'managable' - but no Māori part.
$55 Whakarewarewa Legacy Māori Village Tour and Geothermal Park (2 hours): A 1-hour Legacy Māori village tour, and then the geothermal park including some of the more private bits: $55 per person. 'Legacy' here basically means there aren't people living there now - after all, they live in ordinary houses these days - but they show you how people lived there in its time.
$135 Te Puia 'Te Ra & Haka' experience (2 hours, evening): Village, geothermal and a haka: $135 per person. A sort of souped-up Whakarewarewa - the cost partly reflecting the work of staging a haka for you.
$169 Mitai Village (3 hours, evening): Huge Māori cultural experience including village tour and hangi (feast). May be a bit overwhelming.
Personally I've never felt up to the full in-yer-face cultural things, though people tell me they're incredibly good. My practice is usually to do the geothermal trip at Hells Gate (it's really good), plan to do the Whakarewa cultural tour but then find it's not on or it's fully booked, and then perhaps round it off with the Whakarewarewa geothermal park. And Kuirau Park really is a very good taste of it all.
Whatever you do, just swallow the cost and get on with it. It'll be worth it.