12+ years creatine supplement user here:

Don’t fall for branding. If you have a brand that you trust, go with their product. Otherwise, BulkSupplements offer high quality for affordable price. Especially for creatine, one of the most studied supplements in history. As long as it’s creatine monohydrate, no other ingredients, you’re good. Whey and protein supplements are where things can get shady…

5g-10g daily is the entry point for average weight/height males (3-6g for females).

Optimal dosage is gonna be up to you. Start with 5-10g/day for a couple months, then experiment with more. I’m currently taking around 15g a day with my post workout shake or with a cup of water on days off.

Hope this helps. Happy to share more if you’re curious!