In my opinion you need at least three different things before you can even start to think about creating your very own manager game.
Experience
You have to have a true interest in playing games. It really doesn’t matter if you play a browser based game or you play the game locally(on your PC). Personally I like the PC game better because of their richness of functionality but on the other hand an browser based game offers interaction among the users so my advice should be to gain experience from both kind of football manager games.
Skills
Now the fun part has ended(?) and you need to get some kind of education in programming and database development. Don’t worry, you don’t have to be a rocket science to be able to create your own game, just some basic programming and database knowledge.
In my opinion it really doesn’t matter if you learn PHP, ASP, JSP, an object oriented language or not. It is all the same with different approaches for solving the same problem.
I would say that database knowledge is more important than the programming skills when developing a manager game. If you manage to create a very good database for your game you’ll have a much more pleasant journey in your effort to create the game. Stay alert on your database courses and learn your SQL well!
Go to school and learn some basic programming and database development!
Tools
First of all you need is a plain text editor for programming. It is probably easier and the result will probably be more beautiful with a WYSIWYG editor but on the other hand, when making changes, you might drown in all the code those editors generates and not be able to make the necessary changes. Start with a plain text editor and get familiar with coding is my advice.
The second thing you need is a database for storing all the data the game need. If you choose a free downloadable database or buy a it is a choice I leave to you.
The third thing is a tool to make the game reachable for several people at the same time, remember it is a multiplayer game we’re building. Once again there is possibilities to make it free. There are several freeware to download that makes your PC act like a server, buy a server or find a host that take care of this for a monthly rate. I would recommend that you find a cheap and reliable host to start with. Make sure the host you choose fulfils your requirements you have on programming language and type of database.
Now it is time for you to start working on your own manager game!
As you can see, it doesn’t have to cost you anything at all or at least very little to build a manager game and make it public. That is half of the fun isn’t it? ;)Don't forget to visit Managerglory, for an example of a browser based football manager game