People mightl tell you to 6 star the legendary but i would personally 6 star galek
You have a good hard hitting aoe on 3 turn cooldown and more importantly you actually have a chance of booking galek , better campaign farmer.
Yes. The first lvl 60 should allway be a champ that can farm 12-3 brutal. The starter champs, including Galek, can do that, so he is a good choice. When you have a farming champ, that can run 12-3 together with 3 food-champs, your next lvl 60 will come much faster than the first one.