By best I'm sure that you mean large returns with small investment. LOL
Seven Feathers in Canyonville, OR. Large off-site nice RV park with shuttle service to casino. $$$ Nice, but not our thing. Dry camping available, no charge, just to the north and walking distance, and also in the south end of the parking lot. Decent food. Also a small county RV park just north of casino. (Douglas County) Stanton County Park. Has reservations, decent sites, some pull through.
Near Redding, Win-River has a full hook up lot, don't remember if it charges. Decent enough lot but very rude security. See my review on https://www.casinocamper.com/califor...n-river-casino
"Okay...But." We will never cast a shadow at that place again. Food so-so to OK.
Rolling Hills has a decent RV Park. Food was overpriced but OK. Don't remember too much about it.
Colusa Casino east of Williams was blast for us. Great people, good food, Wife made a profit on the first day gave it back the second. Dry camp only, I think they had plans to expand to hookups. Food okay.
Thunder Valley, Lincoln. Dry lot is a short bicycle ride from entrance. Nice casino but over priced. Only stayed a few hours.
Red Hawk Casino, Placerville. See the few reviews on https://www.casinocamper.com/california/red-hawk-casino
specifically about the entrance. Fun but busy when we were there. Decent food , excellent service for as busy as they were.
If your going the coast route...
Lucky 7 in Smith River. Small but wife usually has fun. Decent food. Great people. See my review https://www.casinocamper.com/california/lucky-7-casino
"Gravel Lot Gone." Been there several times. Last time we spent two nights.
Blue Lake Casino, Blue Lake (West of Arcata, CA) Spent about an hour then left.