You could ask the GBF community on Reddit/Discord or contact Cygames directly. Do take note that the support team is currently only Japanese speaking and can only help if the mail is in Japanese.
Yes, all you have to do is register an account through the Home page. Open GBF on browser through the Official website and connect your account there.
Wind is the easiest element to start with, considering how powerful summon can be bought in Shop and easiest raids, it is the most beginner friendly. It is not recommended to start with Light or Dark as their weapons, summons and raids are the hardest to beat. You can start with any of the four main elements as long as you have strong character for them.
See the Evaluation List for characters. SSR characters with 9.0 rating and above are ones you'd normally use for a long time. Rerolling is another way to get specific characters you want.
A high priority is to reach Rank 30 to leech Omega Raids for their SSR Omega Weapons and complete your basic grid. AP/EP will overflow in early stages due to recharge during rank ups. AP/EP generation slows down after rank 30, here is a list of general priorities to take note of:
Farm Co-op quests and sell the Disks that drop. It doesn't cost AP when someone else hosts. Do the rupie quest weekly. Take Karteria when leeching raids, her skill gives rupies.