Great question, @rachel21! 
Siofra already gave some great advice, so just wanted to pop in and agree with what she said that it is really is all up to you- thereās no āone size fits allā when it comes to travel altars, as thereās no āone size fits allā when it comes to witchcraft! 
My best advice is to take a moment to look back on what you usually do in your everyday practice and examine the things you do most. Can you make these spells/rituals/routines portable somehow?
For me, I donāt have a set kit for my practice per say but I do have containers of favorite herbal teas and herbal medicines 
. Iāve also started traveling with small flicker tealight candles and they are amazing 
. I also bring my crystal jewelry and a few small good luck tokens and charms (like the Travel Protection Pouch) placed throughout my bags 
- and thatās basically it!
Take a look at the things that are most important to you- you can make a fancy box or simply add them wherever they fit into your luggage. No right or wrong way to go about it so long as it works for you 
Good luck and blessed travels, Rachel!