The symbols and colors are more a guide for picking your team. When you're looking for a player, go for players in the same color, and preferrably in the same symbol. Or vice versa (maybe that's even better, since it looks like most teams focus on color first).
Take a look at the teams in your league, so you could get a good idea of the "power level" of the players. Players with ratings over 50 are already pretty hard to get.
The best way to get players when you're with a new team is player swapping. Use the player search option to find players who are comparable, but in the color or symbol you want. Then check the teams these players are with: maybe your player fits better in their team. Then propose a player swap.
Be careful what you buy! Loaning players can be useful as well. Check top teams with like colors or symbols for young players. You already got two players on loan.
Point of attention: sell that 30 year old forward right away. He'll be retiring at the end of next season, now you might get more money than he's worth. Aim high (aim for 3,200,000), other managers will assess his value and give a lower bid, some are just stupid. Don't accept offers right away.