Health insurance - check
Covid Vaccination - check
Hand sanitizer - check
Non-surgical mask - check
Lots of cash - check
More cash or access to a low fee ATM - check (don't carry all your cash with you at the same time)
Camera - check
Good walking shoes (great point
@Lemonzest ) - check
Bottled water - check (CVS has several locations on the strip, cheapest place to buy bottled water)
Sunscreen - check (even in the winter, you can get a burn, unless you stay in the casinos the whole time)
Depending on where you are staying, the Monorail is a good way to get from the South end (MGM) to the North
(Sahara). A weekly pass is a great deal if you will be using it every day, otherwise not so much.
If you want to see shows or attractions, the hotel Concierge is your friend (often same price or even cheaper than the discount kiosks). Also look in your hotel room for coupon books for discounts.
I'm not sure if live shows are on again, but Cirque de Soleil "O" is IMO the best show to see if you are only going to see one. Book early, as seating is scarce even in non-Covid times. Spend a bit extra to get the best seat(s) you can afford.
For singles harvesting, asking at the cashier to buy 1-5 chips will often be met with the question "are you buying them for souvenirs?" . If you say YES!, they will often go in the back and get some minty new ones for you, or at least give you the best of what they have in their till. Sometimes they will send you away, in which case you can buy anywhere from 5-20 chips at a table, and then go to the cashier and redeem the ones you don't want.
Have fun!!!