Waikoloa Beach resort is a pretty good jumping off spot.
From there you can head east on Waikoloa Road (10 minutes away from the resort, with a good supermarket), thence to Waimea and the Belt Highway for Waipopo Valley then south to Hilo, OR you can hop on to Saddle Road across the center of the island to Hilo (they are still repaving near Hilo, but traffic seems to move along.).
You can also bypass Waikoloa village and go north on the main drag, then east toward Waimea on 19.
A lovely drive north, past the harbor and a couple of archeological sites worth visiting, takes you to Hawi and Kapaau, and then to the end of the road, the Pololu Valley scenic lookout.
To the south, it's about 30 minutes to Kailua-Kona, where there's Costco, Safeway, Target, Walmart, etc.
Waikoloa Resort area has two small shopping centers (King's and Queen's) with fast food, a few nice restaurants, galleries, the Island Gourmet market, and ABC; also fairly frequent free performances/concerts.
I like to avoid Kona traffic, frankly, even though it's far better than it used to be; unless you are going to snorkel Kealakekua Bay or Place of Refuge, it can be easier and faster to go north around the island (from Waikoloa area) to get to Hilo.