I've only day hiked to the first valley past Waipio. From the Waipio lookout, look for the switchbacks going up the far wall to see how far inland for you to go at the far end of the beach. Carefully choose your crossing of the stream at Waipio. Hang out for a bit and watch where others go. The mosquitoes are bad as soon as you step away from the beach breezes, until you get high enough on the far wall to regain the breeze.
On the trail, I met someone who first visited, then turned around, then chose to walk at my speed. I assume that he was a local with a nearby pakalolo crop that he was protecting.
At Arnott's Lodge, a hostel north of the airport in Hilo, you can use your tent on the grass for $10-15 a night, rent a bike for $7, catch the bus for a dollar at the corner, etc. DW and I stay there in the bed-with-bath rooms with shared kitchen for $75 a night. Arnott's has the whole spectrum of lodging from the lawn, a few dorm rooms, private rooms with bath down the hall, rooms with private bath, same with shared kitchen, then $100 a night rooms with private kitchen. The tall, slim older guy you see walking around is the owner.
On your first visit, go ahead and spend on the tours. After that, you can go do the same tour on your own if you have a car. We are going back for our fourth visit next month.
Happy trails to you. There's probably some Hawaiian lingo for that.