I think it's important to realize that the importance of preschool is not to teach numbers, letters, etc. Academics is NOT important. Preschool teaches kids to separate from their parents, work or participate in a group, and negotiate their own space without hitting! That's all that's necessary to prepare a kid for kindergarten.
There's a lot of emphasis on preschool in many communities, but I have a neighbor who has not sent her child. He'll go to kindergarten in the fall, and he's done fine by playing with kids in the neighborhood, having play dates, going to story hour at the library, going to free activities like the petting zoo at the local garden center, and so on. He separates well and can be at the neighbor's house without his parent present, and I know he will do fine in kindergarten.
You don't need to home school any farther than you already have. Instead, get your child out of the house and into social situations, situations where she has to follow directions (e.g. lining up is a hard concept for many kids!), places where she has to cooperate with other kids, and so on. That can be as simple as neighborhood play dates (go from 2 kids to 4, to 6, etc.) where they have to speak to get along and to communicate. Go to playgrounds and have her play with kids she doesn't know. See if she can follow directions from the children's librarian - go to story hour but sit in the background so she engages with the story-teller. If you go to the local children's museum (libraries often have passes by the way, so you don't have to pay), then encourage her to sit in the little programs where they show a live animal or do any other educational program.
I don't know if you want to pay for Gymboree if you can't pay for preschool. But that's your call.
Get her outside - she what she can observe about the weather or the scenes around her. A lot of preschools do "circle time" and include talk about the weather - is it cloudy or sunny, breezy or still, cold or hot? You can discuss those concepts in your own life.
Kids also need to learn to adapt to changes in schedule. So getting your kid to clean up her toys before you do arts & crafts, or cleaning up her snack plate before going outside, etc., are helpful skills.
Overall, based on my experience with early childhood educators, I'd say not to worry about academics at all. That's not what teachers need! They need kids who can cooperate, who are inquisitive, and who have some skills in fine motor and gross motor areas, who like to be read TO even if they can't read themselves. Kids who can read don't necessarily do any better than those who cannot. Kids who can't share and who can't follow directions are the ones who have the most trouble, as well as kids who are bored with letters and numbers because they've been drilled too much at home.