All you need is a ripe banana and a fork. Cut a few pieces and mash it with a fork until most of the lumps are gone.
Just slice a few pieces of ripe avocado and mash it with a fork until mostly smooth.
To make peach baby food at home quickly, just peel a very ripe peach, take a few slices and mash with a fork until very smooth.
I use the same oats I would use for my older kids. I do often mix in some juice or other mashed fruits (like peaches, pears, applesauce, or bananas) for added flavor.
Just bake or boil a sweet potato until soft. Remove the skin and mash with a fork.