Does it mean im lacking a vitamin or dehydrated if my tongue gets dry on both sides of my mouth?...

Probably not: If you feel dryness in your tongue only but nowhere else, i doubt you are dehydrated or have a vitamin deficiency. Mouth dryness is a frequently reported symptom, but it lacks specificity. Diabetes can manifest through dry mouth, mucosal atrophy (thinning) can do it, too, acid reflux can be a culprit. I'd suggest a comprehensive history taking and physical exam to begin with.

Maybe: It could mean you are taking medication. Most medications have dry mouth as a side effect. It could mean you have an autoimmune disease. Lots of reasons, check any medications for side effects, sugar free gum or canndies can help, avoid alcohol ie listerine, if things don't return to normal in a couple weeks, talk to your dentist or md about it.