Strategy to succed in all competitions

I am currently Level 2, season 2 after finishing 1st place in the league last season. I usually play 4-3-3 defensive, hard tackling, forced counterattacks. As of today I only had one defeat this season in the first cup match (3-2 final, 3-0 halftime, home match). At halftime I changed tactics to defensive + counter attack after using attacking. It was a match agains a way weaker team. In the 2nd leg i managed to win 6-1 away and qualified for the next round of the cup.
I got 2 draws in the league after my top striker (5 stars) got injured. I managed to win 2-1 away in the 1st leg of the cup 2nd round without him and after I healed him I won 9-0 in the 2nd leg home.
The problem is that I don't know what competition I should focus on. I have the best team in the league, and one of the best in CL and Cup. Everyone says that the best way is to focus on the League, then CL, then Cup, but i'm not so sure about it. Currently the Cup is the only knock out competition and it's very important for me to do well in it because it has the biggest prizes. I'm pretty sure I'll finish the first in the CL group, this is very important also, because if I finish 2nd I'll have to deal with a strong team in the first knockout round. In the league the 2 draws with pretty weak teams made me think a little, but as my best striker is back I hope I won't have problems from now on. I think I should continue with this strategy, and I will not change it unless more negative results in the league apear. What do you think?

in my experiences, in any game attack is always better. A non defeated season at level 1 say nothing (i have 17 win 1 draw). I agree Cup for me is the most important. My team is far better than others in league and champion league (only full 5 * 1 scout.) but the Cup we have the same quality opponents, winning the cup is far prestige than the other 2

So far I've not had a defeat in either League, Champions league or Cup, but I do feel like getting knocked out of the cup because I know I can't win it, but I have a real shot at the Champions League, I am probably going to play my worst side possible for the Qualified Legs as I want out of the cup.

You need a full side (I think its 25 players all together) to compete in them. I've done alright with 15 but I'm not aiming for the cup.

Currently Level 7.
5 league championships (missed season1 when I played only 4 games, and season 4 which I deliberately sandbagged to try and get a better Cup draw under old format),
2 Champions League championships and 1 second place finish in 4 tries.
1 third place cup finish* in 6 tries (Cup Level 9[2], Level 9[3], level 10[4], level 8[4]*, level 8[5], level 9 [6])

Does that count as successful?
I play my best 11 in Cup and CL, play my 11 scrubs in league.
I play defensive /counterattacking (3-6-1 V variations) almost all the time except against a couple particular formations. I usually have the league's top scorer, the most goals and best goal differential by a wide margin.

I don't buy tokens - I spend about 70-80 tokens/season on transfers (picking up 35-45 tokens from videos, offers), always buying top 5* players (as close to 6* as i can find) with multiple positions (DC/DR, AML/ML, etc.), never worry about SAs. Keep 22 or more players on squad. I usually stomp on all-out-attacking teams because they're so predictable and easy to get possession advantage over.

My strategy? massive squad turnover each season, use formations and tactics to 1)gain local advantages onfield (e.g. 4 defenders vs 3 attackers), 2)gain possession advantage (always outnumber opponent at midfield) and 3) exploit weakness (e.g. attack middle with AMC and lone ST vs 4 wide defense). Focus on Cup, then CL, don 't worry much about league.
Your mileage may vary.

depend on league .. in my league is so tough , i have a mate who always try to match me and buy scouts and in past 2 season we are 4-5 good teams .. and every point dropped will be costly .. so can't afford to play 2nd team in the league.. i play 2nd team in cup bcz stupid server put me with guys who have 7* & 8*, in CL i only play my first team if opponent is stronger which is often in knock out stages