Best way to Grand Canyon, Yosemite, Yellow stone for solo traveller (not by tour)

Hi guys,
I will travel alone for 14 days start from LA to 3 national park Grand Canyon- Yellow Stone- Yosemite and end up at SF (Aug 24 or 25 to Sep 7). I only have budget for 100$/day (include everything). How can I travel that route easy without taking a tour, I really dont like to get a tour, prefer adventurous trip that I stay in camper van or tent and doing a lot of hiking. I am looking for buddy to travel with or sharing the camper van. If you know any website to find traveller to share the camper van and share a ride, please let me know.
This is my first time to US, hopefully i will have amazing time there.
Thanks for all your advice.

Hello and welcome to the RTA forums !

If your budget is to include vehicle rental and gas and a place to sleep it is going to be extremely difficult. There is no way it would afford a camper van without travel buddies so it would be a car and tent going solo. I would look to see if there was a way to raise that budget so that you can have an amazing time without concern. Yellowstone is quite a distance from the other attractions and there are many great National parks much closer in southern Utah you could consider. You may also find that flying in and out of the same city and dropping the car back to where you collected it, might save money.

You can start a thread in 'Share the Gas' forum to try to find travel companions.

Please be aware that your vacation time includes our three day LABOR DAY weekend. Many campgrounds are already sold out, especially the National Parks. Do a little research now to avoid problems later.