My 18 year old is a simple guy. He’s not worried about matching anything or even too worried about what he “needs” for his dorm room. In fact, other than the basics he’ll probably just go get what he needs with the few target/Walmart gift cards he got as graduation gifts. So … the one thing I have this underlying urge to get him is a nice mattress pad. But I don’t want to spend a fortune. But I do want him to be comfortable (the kid can sleep on the floor). Ha! Anyone else have this need to make sure they are provided for and comfortable when you know they will be fine?? And seriously, anyone have a good recommendation for a basic mattress pad that doesn’t cost an arm and a leg? I’m thinking mattress pad, pillow, sheet set, and maybe a cheap comforter or blanket in case someone wants to sit on the bed. And a shower tote. He got a set of towels for graduation and a few basics (Tylenol, ibproben, a couple bowls, utensils, salt and pepper, etc). He uses his phone as an alarm clock… Probably a fan.
There are sheet & comforter sets available cheap, but a lot are all polyester, including the sheets, which many people find uncomfortable. Check out Marshalls, TJMaxx, & Bed Bath & Beyond for some decent cotton bedding. He won’t care if anything matches, so pick & choose individual items on sale.
Experience tells me he is highly unlikely to use a shower tote.
If by “mattress pad” you mean “memory foam topper”, get one at least 2" thick. Good ones aren’t that cheap. Stay away from the “egg-carton” style latex foams ones, they don’t provide a lot of cushion and will fall apart.
Make sure you check what size bed he will have. Many schools use twin XL mattresses, and these sheets are harder to come by.
Buy the cheapest sheets you can, and be prepared to burn them after his freshman year. Odds are they will not get washed more than a couple times, if that. Unless he gets a girlfriend. 
Bed Bath & Beyond will have twin XL sheets and mattress pads. If you can buy with one of their 20% off coupons you’ll save money.
Our daughter uses a memory foam topper and it makes all the difference in her dorm bed being comfortable. BB&B has those too, or you can look on Amazon. The are are blue gel foam ones that are cooler than the regular memory foam.
Here is one:
https://www.amazon.com/gp/product/B00FJNQA1G/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
Kohls had a great sale on the toppers this week and we picked out a 3" memory foam topper (blue) for about half price and got $30 Kohls cash we are going to use for towels.
@momocarly - thanks! I’ll go check that out!
@notrichenough - yeah, I’ll wait on the shower tote. Someone had told me he would need one, but I’ll let him see if he does. He has target and Walmart gift cards he got as graduation gifts 
Yes- they have XL beds so have to get those sheets for sure.
Twin XL sheets will be plentiful starting this month for all the college sales. I got DS a well priced light quilt set at IKEA “Karit”. I got a mesh tote at BB&B since he will use a shared hall bath. The ones at Walmart were too small. BB&B will have college shopping events, with remote pick up available, and I think 20% off everything for the season. I think you may be able to stack coupons. I got towels already at Ross. I hate pills on sheets and will get some plain cotton ones, a mattress pad, pillows, and cover at BB&B.
My DS is like your son but he understands that I need to do this for him. I will have to wait until my DDs go to college to go all “Hotty Toddy” decor on the dorm rooms. LOL!
I got my kids inexpensive “egg crate” mattress toppers as well as a mattress pad and they were just fine.
California D did not care about a thick foam mattress but loved her heated one during NH winters.
The twin XL mattresses at most colleges are very thin! Like 4 inches deep.
I’d recommend getting him the best, thickest mattress pad available at BB & B.
And dont forget he’ll need deeper sheets to accommodate the extra thickness!!
He may also want an egg topper as well, but that can be bought later.
This assumes he will be making his bed. 
My sons used a caddy like this for the showers that were down the hall.
https://www.amazon.com/gp/aw/d/B002L2Z93I/ref=psdcmw_2422451011_t1_B00KGGIR7Q
All three kids used xl twin eggcrate style toppers from target, around $25.
https://www.target.com/p/comfy-foam-mattress-topper-room-essentials-153/-/A-52116775?lnk=rec%7Cadaptpdph3%7Cviewed_bought%7Cadaptpdph3%7C52116775%7C7
They also had mattress pads that went over the topper and under the sheet. https://www.walmart.com/ip/Mainstays-Extra-Thick-1-Mattress-Pad-White/38193297
here is the shower tote I got. The outside pockets are a nice size. https://www.bedbathandbeyond.com/store/product/mesh-shower-tote/127960?skuId=42491736&mcid=PS_googlepla_brand_brand_online&product_id=42491736&adtype=pla&product_channel=online&adpos=1o1&creative=45758750869&device=t&matchtype=&network=g&gclid=CjwKCAjw-ezKBRAGEiwAu-_-LDz5H2JooWUZ5SyQjHKc2fuYqNYArbiCCTw7BXhhB_W69V6EqrjfXBoCdZ8QAvD_BwE
I’m thinking about one r two of the egg crate pads since DS will need to store all this stuff over the summer and those are thinner. I would also be much less likely to fuss if he had to disposed of a cheaper one.
One mother told me she bought several fitted sheets and put them all on the bed on move-in day. Then her son could peel off the top fitted sheet for something cleaner.
Don’t wait too long to buy the XL sheets because when they sell out the stores do not replenish their stock.
^ yep, I did that on S’s bed with two fitted sheets.
The mattress toppers make a world of difference. And don’t be tempted to open it before you get to the dorm room. They are at their most compact when they ship. DS loved the one he has from Amazon.
I doubt his sheets were washed frequently but I did buy a second set of pillowcases thinking that they can have a big impact on skin health.
Or… attempt to teach him to wash his sheets more than once a semester. Hey, it could work!
My family isn’t into the foam stuff, so my kids have always used something like this - you can get down or fiber fill. Mattress pad on mattress, followed by one of these mattress toppers than a sheet. Super comfy.
Does he want a fancy foam (or other sort of) topper? Didn’t sound like it, from the first post. After all, you said he could sleep on the floor. Some guys’ egos can’t take all the schmancy their moms want to set them up with. Lol. Just saying. In that vein, I don’t now if guys want to walk down the hall with a caddy. How much will he be carrying?
But I have girls. so maybe I’m wrong. (And they didn’t keep the caddies, either.)