Ive been told Tá an saol go hálainn and Is álainn é an saol and would like to know which one is the proper way please!

Actually, they both work.

Tá and is are different verbs (or, technically, tá is a form of the verb "to be" and is is the "copula", but I assume you don't want all the grammar explained). Tá and is are not interchangeable, and the basic way to say what you want is the form with tá, but the second phrase, using is, is a way of emphasizing the adjective, with a meaning something like "It's beautiful [that] life [is]".

Note that saol can also mean "world", depending on the context, and there's another word for "life", beatha, and some might feel that it's a better choice for your phrase, because it is often used for "life" in the abstract sense and using it would eliminate any chance of your phrase being understood as "the world is beautiful". If you choose beatha, then you'd have the following (the differences shown in red are for grammatical reasons, and represent pronunciation changes as well):

Tá an bheatha go hálainn

Is álainn í an bheatha

The word beatha is the one used in the Irish term for whiskey, uisce beatha ("water of life").

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

I would use the copula here. I'd also point out the (subtle) distinction of saol vs beatha. Saol is mroe like life in general and living, beatha being more about "life-force" (can't think of a better word?).

Is álainn é an saol
or
Is álainn í an bheatha

are good IMO.