@akuataja
Thick is a very broad term and defining what you want to achieve might help you get some responses (Do you want to suspend something? is it just thickening? must it be a clear gel?)
For a gel with only one thickener, I would go with the dehydroxanthan gum - It does however not gel enough to suspend particles and is more sensitive to electrolytes than regular xanthan gum, so beware of that.
You might also want to try a multi-component gel (Binary often good enough great, meaning you use two gelling agents). As Pharma mentions Xanthan has synergies with Locust bean gum and “similar gums” - similar gums are galactomannans and guar, fenugreek and tara gum also fall in the same category.
edit: formatting