1: Never force the player to buy something just so they can keep up with the competition, everything in the game that changes gameplay, the player should be able to get by just playing the game and not spening a singel cent on it. You want to make the player want to buy something not force them.

2: You can use commercial ingame to make money instead of ingame purchases. I can't recall I have seen this in any game that is not a mobile game so I really can't say that it will work.

3: To make people "fanatic" you need them to be coming back every singel day to play the game. Here the balance in the game comes in. You do not want to make a chess like game with perfect balance because then you won't need to balance the game. Why do you want to make balance changes all the time? Because that require patches, people love patches and people love when a game changes the meta, because then they can discover the new strategy that work for that patch first. Extra Credits talks about this in one of their videos, worth a look. http://www.penny-arcade.com/patv/episode/perfect-imbalance

Cheers!

As ShiftyCake points out, vanity items is a very good way to make revenue in a F2P game.

Selling items that directly effects a players ability in the gameworld is risky to say the least.

A reason why many people are wary of F2P games are because of the unbalance these purchasable items causes.

Some of these F2P games are even refferred to as a P2W (or Pay to Win) games.

I must say that I dislike the way you are talking about your potential players.

how to make user eager to buy paid item continuously? how to make them fanatic?

If your aim is to make "users" fanatic in order for you to make money, I suggest not making a game at all.

you know,,, with no money, no devs, means poor quality, or break down of team or company.

You never enter the gaming development world with eyes on getting rich, you mkae games because you love it. If you can make a living on it, good for you! But you have to put that as a secondary "objective". Yes, making games cost money, alot of it, it's a sacrfice we do as developers.

If you are only after the cash, enter a business school and educate yourself to something fancy and join EA Games as a Production Manager, they don't know shit about games but they make alot of money :P

Extra Credits talks about this in one of their videos, worth a look. http://www.penny-arcade.com/patv/episode/perfect-imbalance

This is an interesting video. What I really got out of it was that you want an evolving more complex rock paper scissors game even though players always seem to complain about rock paper scissors games.