These tips are NOT for everyone but you asked for some ideas. Here are some I have used. Get a Disney credit card that has a spend $500.00 in three months get $200.00 back. Buy gift cards with the Disney credit card. Thus you get points to turn to cash to spend at Disney and get the cash back reward after spending $500.00 in three months. Plus you get Disney cash for other purchases and charges of everyday life. (This plan will only work and save money if you pay your cards off at the end of each month.)
Or buy and pay with Disney gift cards you purchase at Target. I believe a $50.00 card for $47.50. Sam's Club has a similar deal. (Friends I exchange gifts with at birthdays and Christmas have bought me Disney cards before. They know we go frequently to WDW.)
Don't stay on a Friday or Saturday nights as rooms are more expensive. Upgrade hotels: Really depends on what you mean per upgraded. We normally stay at GF or CR in the main buildings. I traveled to WDW in May of 2019 and stayed at Pop by myself as I wanted to go to the Garden Show. Yes, there is a difference but the Pop room was almost brand new, I loved the walk around Hourglass Lake each morning, the outdoor bar area with music was great in the evening, and there was a large food court area. (I packed half the clothing etc. and did laundry one night so I had no bag fees on my flight. Laundry is right by the food court. )
I bought bottled water for the room and took one each day to refill in the parks for free. I ate an energy bar for breakfast and then ate one meal in the afternoon and then had a snack in the evening. I would not be so frugal if I was traveling with my significant other but it worked for me. (He is 6'6" and a breakfast lunch dinner type guy!! lol) Also, don't forget you can order off of the kid's menu which I do when traveling with others eating three times a day. I also received a $60.00 gift card since I did not have my room cleaned but no idea how they are doing this with Covid protocols.
This trip almost became a game to me to see how little I could do an eight day trip for in terms of $$$.

With my free airfare using points and what I have mentioned, I spent just under $1,400 and this included three Disney Tours, High Tea at the Grand Floridian, The Epcot Garden Tour and the Behind the Scenes half day tour at MK. Like I stated: This is not for all but it worked well for me and what I wanted to do on my solo trip getting a bounce back price from our January trip. I also scheduled our Christmas trip while I was there to get the bounceback price for our stay at the CR. And I should mention I did have an annual passes. And yes, I am going through Disney withdraw.