Here are my tips, coming from out of town (flying)
1) google flights to track flight prices. Wait for a price you are willing to pay (I saved over $200us last year and about the same this year)
2) work for someone. This often includes your badge and hotel (and some pay on top). True dungeon is always looking, as are many others.
3) breakfast. If the hotel doesn't include it, go to the grocery store (2 downtown) and pick up breakfast bars and some fruit. I aim for about 400-500 calories for breakfast as it will be a long day.
4) lunch / snack. Go at least 2 blocks away and get sit down food. Just about the same price for better food and often more food. Alternate option is bring granola bar / cliff bars. Looking for around 300 calories. Nuts are also great.
4) dinner. Get something nice if you bagged your lunch, you saved money already, and you have the calories for it. If you had a big lunch, consider something small (I mentioned grocery stores, right?)
Demos are free in dealers hall.
Lectures are free.
Writers symposium has a lot of awesome stuff. Don't be afraid to spend $2 or $4 for events you want to try. Game library is great, and there is the mayfair/asmodee stuff (caveat, this may change)
6) controversial methods:
Ok, so these are not great, and I advise against them, but you could... stay up all night playing d&d rather than a hotel room, use wet wipes to give yourself a quick wipedown in the mornings in the bathrooms. Sleep where you can during the day, or power through. Do not do this, but I have seen it done, often with stinky, tired results.
In 2018 I spent under $1k on gencon, including a $300 flight, by using the advice above, and that included spending about $400 on dealers hall.