Aradia: Two sets of adventure themed mixes and tracks, two sets of toe socks that are both time related with clocks and gears on them, and a mix that's centered entirely around time. You hear the winding of gears, the tick tocks of clocks interwoven among the bass drops and
Bro: A dark gray shuppet wool scarf, a mixed track to show Bro all that he's learned since he's seen him last, and a Growlithe egg.
Dirk: Ponyta egg (Egg Moves: Captivate, Hypnosis, Charm, Growl, Toxic, Iron Tail, Swift), plus flaffy lined boots because dude you're gonna need them, and a couple mixed tracks centered around fire. Hey it will keep you jamming while you stay warm. You'll hear Rapidash in the mix because she helped out with the fire part.
Eridan: You know he actually got you something. A purple pageboy cap because you need to look more like a tool than you do already.
Jade: A series of mixes of his usual stuff but centered around snow and ice. Yes, he recorded the noises of their doom and turned it into sick tunes. Plus arcanine themed earmuffs.
Jake: Knee pads. Seriously, you need these badly. Also a helmet. You need that too. These set one inside the other along with a book 'Ruins of Alph'.
Jane: First, a new baking spoon, a shirt 'Hop to it!' featuring bunnery , and a pair of bunnery themed gloves.
John: With the help of the others? KEYBOARD. Along with a shirt that says 'you don't stand a ghost ('haunter here') of a chance.
Kanaya: Tea, because you're a classy lady and long green scarf plus matching earmuffs, the band being the green part.
Karkat: The music he gives him starts strong, then the bass gets dropped hard, it goes on for a little bit of silence and rises new bits of sound being added until it's this symphony that rises to the finish. You're also getting a dragonair themed scarf.
Mom: ...Man what do you get your mom? Especially when she has no idea you're her kid. Well for one a warm coat, hot chocolate mix, and uh a set of mixes each testing out a different theme. It's almost shy that music, like he's testing the waters of your audio tastes.
Rose: For one, a hug. Yeah that rare thing. A thing of cinnamon candy canes + hot chocolate mix because he can never be normal, and a dark evening dress that's carefully wrapped up with a hastily scribbled note 'knock him dead with this'. He thought long and hard of how to say he loves you without saying it and something that's practical. So date dress. Yeah.

Cross-Canon:

For one, everyone who's ever talked to him gets a travel mug for your beverages.
Reid: A sturdy all purpose journal with a snap to hold it closed, included with it is a couple pens and a travel strap. Investigate away man.
Riku: A book of S word heavy tongue twisters. Go get him.
Cheria: A thing of hot chocolate mix and an eevee mug to use it in. Good luck with Eridan.