Since you’re interested in cost-saving tips, here are a few that I can think of.
Definitely purchase the refillable mugs. They’re similar to the WDW ones and priced at $19 and include soda, tea and coffee. You could probably just buy two mugs and take it in turns using them. Plus they’re a souvenir!
Ulu Cafe does really good pizza for $23. They’re large too, could feed a group of four. By far the best value meal on property.
At the shops outside Aulani there’s a store called Island Countey Market and they have a restaurant quality kitchen serving take out food that is superb. At Aulani, we loved the coconut shrimp which was $16 for 4 shrimp and fries. At Island Market it’s $9.95 for 8 shrimp and rice or mash. My wife and I split one and it was plenty - $5 a head! They also do burgers and the like for less than $10. There is also a good selection of grab n go items like sandwiches and sushi. There are tables outside where you can eat it and it’s just lovely. Beer, wine and spirits are also reasonably priced there (well, they are by our New Zealand prices anyway!).
When we were there they were offering $250 resort credits if you took a tour of a DVC Model villa. I’m not sure if that offer is usually around, we didn’t take it as DVC wouldn’t work out for us but something to consider as it would pay for a few meals.
If you want to get to a Costco, Walmart or Target to buy souvenirs or chocolate macadamias, grab an Uber to Kapolei, it will cost around $12. There’s also a bunch of chain restaurants there like Chilis, Denny’s etc that are cheaper than Aulani.
For getting from the airport to Aulani, Charley’s Taxi offers a flat fee of $55. Uber might be a bit cheaper.
Will add more if I think of anything else.