As with Modern Art, you need to know when and what to buy and when and what to sell. On the surface the game looks like one of movement, but it is really about opportunism and financial judgement. Going back to the Star Trek allusion from earlier, this is a game for a Ferengi rather than a Vulcan. There will be shops with more than three or four customers, but not many. Shops near the gates are more likely to attract custom than shops in the centre, particularly if they are on the natural route from the gate to a different coloured shop owned by one of your rivals.
More yellow tourists means that yellow shops are potentially more profitable.
Keep an eye on how many shops of each colour have been opened, as it obviously affects the potential worth of new shops of the same colour. If there isn't an obvious immediate profit to be made from moving tourists, consider auctioning a shop of an under-represented colour. If there is a group of two or three tourists of one colour being shepherded towards a rival's shop, see if there is an alternative destination that you can put on the market. The bidding for it should be brisk, you will gain a commission and the risk of a financial killing by your rival will have been avoided. In summary, the game is a themed abstract and because it involves pawns moving round a board, the abstractness is more apparent than in many games.