I once thought that if I counter the opponent's tactic every game I would win every match. The truth is that doesn't happen. Had and saw games in which exactly a counter tactic loses badly, of course had games that win with difference, but again - it's not a certainty
Now on lvl 20 I can see only a few almost sure patterns:
- Best tactics to play are 4-1-3-2 (3mc), 4-4-2 or 4-2-2-2 (mc-mc /aml & amr). No idea why, but in the last days of the season I check almost every player from my friends, champions league and cup to see what is the best team in their league and most of them play this way.
- Best players to buy are the most expensive as they grow faster. You may already know it.
- Important players in terms of special abilities to have are AM's Shadow Strikers, FK striker, CS any player but mainly striker and aerial defenders.
Explaining: The shadow striker has immense scoring and assisting every season, best of my players for 4 seasons now.
FK striker (of course logically already has more attacking than anyone else in a team, first because of his stats when he comes out of the shop and second because we tend to raise his attack) is almost every time the top scorer in a league because a lot of goals come from free kicks.
CS striker for the same logic has high crossing and almost always is a top assister
and for the Aerial Defender - I don't know why they tend to be so good but in my league last season there was a team that on the 15th round had GD of 36-2 with 4-starred full backs who were 10-12 quality behind his CD's who were aerial defender scouts and the guy just didn't concede.. He conceded twice in 15 matches in a 5-2 win and i don't remember if he had played both of them, but every time he did - he was immortal. I bought a defensive wall scout for DC before i knew that and although he is good, I can't really compare them.
Did not see any effect of playmakers, dribblers or PK specialist (penalties are rare you may have figured it out already). One-on-one scorers and stoppers sometimes do good - I prefer having this kind of player.

Maybe I'm not telling you anything new but for the reality of the game and my 20 seasons of playing this is what i can help you with

If I had a chance to have an all-scout team, I would play:
---------ST (FK)--ST (CK)--------
AML(SS)-----------------AMR (SS)
-------- MC(any)--MC(any)-------
DL(DW)--DC (AD)--DC (AD)--DR(DW)
------------GK (1on1)