As Kate said, I wouldn't be cutting back on bottles until at least 9 mo (waiting until 1 yr is even better). Formula or breastmilk should continue to be your LO's main source of nutrition for a few more months. They're both higher in fat and more nutritionally complete than any combination of solid foods.
We started trying cheerios with Tyler around 8 or 9 mo. I'd put a half of one in my mouth or in some water first to soften it, then I'd put it in his mouth. He gagged the first few times, but did fine once he got used to it. After that, I'd keep a few out on his tray for him to play with and try to pick up. Good luck!