Nice game!
I see three things in this game.
First, the gamble mechanic is easily exploitable so you never feel real risk. You can high the chance of a wrong number to like 10-20 and just play 4 numbers to get lots of cookies easily, and if you get a wrong number, that doesn't matter, you only pay one cookie to play. To fix this, would be cool to have to pay more cookies for more wrong numbers, and also you could make the player lose cookies if they get a wrong number.
Second, there's no point on buying more chairs and tables. Yes, this way you can have more customers, but in reality what keeps you away from making more money is not the number of costumers but the time you waste making cookies or walking to the costumers. To fix this would be cool to have upgrades that allows you to move faster or to produce passive ammounts of cookies, or maybe add an upgrade that makes the cooking mechanic riskier but more rewarding.
Third and last, I didn't know why my money was desapearing till I notices that it was being spend in more chairs and tables. To fix this would be nice to confirm these purchases in some way to comunicate the mechanic more crearly to the player.
I'm not an expert but maybe these suggestions could make your game more enjoyable. There are planty of ways to adressing these issues anyways.
Well, that's it, have a good one! :D
P.S.: Please try my game, hehe!