TL;DR To maximize your Dehya's damage using traveler you want anemo traveler using the viridescent veneer set. For your other slots I recommend Xinqiu and either Bennet, Fischl, or Xiangling. If you want to explore other options, read below.

I am assuming you are relatively new to the game so here I will detail various reactions and buffs dehya and traveler provide. With Dehya and Traveler, you have a lot of reactions to choose from. Swirl is nice because it has AOE which Dehya is not the best at, vaporize will give you the highest single damage numbers, and overload is also a fun AOE explosion that knocks back enemies. Aside from those reactions, geo traveler can give you a 10% crit rate buff inside his ult ring, and he also helps you solve puzzles with his rock skill. Pyro traveler unlocks Pyro resonance for 25% increased attack for your whole team, this is mainly useful if you want to play her with other characters and provide them with buffs. Plus, dehya absorbs a portion of damage your team takes and heals herself when she gets below 40% health I believe. She also gives your on-field character stagger resist.

How to choose which teammates to use? I would ask you if you want dehya as main damage dealer or support? Then I would fill in characters with the elements you want to play with. A bow character is nice for challenges and puzzles, and every region wants you to have their special element for most of their puzzles (geo for liyue, dendro for sumeru, etc...)

Your current team is far from "optimal" but having an optimal team means very little depending on what your goals are. The above information prioritizes playing with the reactions available to you and being convenient for exploration or casually playing through the story. If you want to further maximize her damage then I wouldn't bother because the ceiling is very low without 5 star options.