Wow this all looks to have a life of us own for such a simple answer.
**. You do not need Matchday Membership to get a ticket. ** For more answers read on...
If you want to buy directly from City buy
MATCHDAY MEMBERSHIP
If you want to pickup the odd ticket just register for the free Citizen Membership.
Advantages: Matchday membership as you will get immediate access to all games, including Champions League/League Cup/Fa cup - only one ticket per account though.
You can still add extra tickets to you account obtained from others.
CITIZENS MEMBERSHIP
The membership number allows those with an available ticket to add you to their 'family and friends' in order to send you the ticket.
The ticket will then be found in your City account. City will email you with a link to add the ticket to your phone's wallet. Alternatively, from your account click 'download ticket'.
Sometimes you may not be added to F&F but will be sent an email with just the link. In this case add the ticket IMMEDIATELY to your wallet.
Once a ticket is added to a wallet only you have access to that seat as the link can be used by others. BE WARNED.
Using the same account you can have multiple tickets for the same game. If your multiple seats are not accessed thru the same gate then you can send the emailed ticket link to others to load into their wallet
finally enjoy the game