Welcome to the community!
Currently it costs 1 Ark to vote/unvote for an Ark Delegate and only 1 address can vote for 1 delegate at a time.
If you want to vote for multiple delegates, you will need multiple Ark Wallets.
Your Ark Wallet balance determines your voting weight. 1 Ark = 1 Vote.
Say you have 1000 Ark balance, this means that your Ark voting weight would be 1000 Ark.
There are only 51 Ark Delegates that can actively forge. Some are private but most are public pools. I would recommend reading through Ark Delegate proposals to view and determine which each delegate offers in return for your vote. Here is a list of Delegate proposals on the ARK.io Forum. Also, you can use profit sharing calculators to help give a rough estimate on expected payout.
Have a great day,