Entering each pool should be justified. Sufficient reason is of course the combination of cards, which gives you a high probability to win the pool.
A combination like this mentioned above can consist of two pair of Aces and all the elder combinations. However, if you do not have good cards and you are forced to buy some new cards, then you have to concentrate on the cards you are buying. It means for the all players that the less you change or buy the cards, the higher pool should be fixed, to even out the level of the risk taken. Your engagement in the game should be up to the relation between taken risk and probability of winning the pool. It means that if the achieving a desired combination has 20% probability, the pool should be at least five time larger than the money you invest in the game. Otherwise, he entering the game is not profitable.
An example- your opponent has four, each following the other one, cards, in the same colour. The cards, however, neither are the eldest in the pack, nor the youngest. This allows the player to get a straight or a poker, if he is sufficiently lucky by buying the cards. The easiest to get is a straight, which come statistically once three times. In this case, if other four players enter the game and the pool rises four times, it is profitable for you to take your chance and play. Anyway, you can buy a card to get a colour in your cards or a poker, what raises your chances regardless of other players’ strategies.