I would recommend avocado for a first food. It's got everything you need, healthy fats, fiber, vitamins and minerals, etc.
I did store bought baby food for my son and he had horrible allergies. The dr. said it was the ascorbic acid. So with my daughter I did home made baby food. I have a "magic bullet" food processor, which was my method of thinning it out. I basically put the fresh veggies (green beans, broccoli, frozen mixed veggies) in the jar with some water, put the steamer lid on, microwaved for about 1 minute, drained most of the water off and then changed to the blade lid and processed it. Then I divided it up into an ice cube tray and froze it. When she was first starting out, 1 ice cube of veggies was enough. As she got older, I made it thicker and gave her 2 ice cubes of veggies. Some combinations I did with success were:
plumb, pear (I did these fesh, no cooking, just wash really well)
Apple, blueberry
Banana, grape
Apple, grape
Veggies I just did alone, cooked in the microwave
Carrots and beets are really good mixed in with the veggies. It was way cheaper making my own. I would suggest buying a few jars of store food for convenience, like if you eat Sunday dinner out or something.
When my daughter was about 9-12 mo, I started just cooling a bit of the dinner I made for the family and blending it all together as her serving. Sounds so gross but she loved it. Something like Salisbury steak, green beans and mashed potatoes...looked nasty but she ate it up!