I wouldn't recommend downloading tactics. To me they are completely useless as they don't fit with the style I want my team to play. I use to play with downloaded tactics as I had no clue why MY tactics didn't work and sucked so bad I lost every single match... But over time you will figure out how to put your own tactics for the best of your team.
My tactic selection priority is the formation... Usually your Assistant will tell you what 3 formations are best suitable to fit your squad. I would use that as a starting basis. (My asst. suggests 442, 4411, and 4312... So I've got that down)
Now you play with it a little... I base my tactics on my best 11... Say if my 2 striker are one an right footed Advance Forward, and the other one is a left footed Poacher, I will put that down.
My tactics are simple... Very simple. My 442 pretty much consists of:
2 Limited Defender (Stopper)
2 Full Back (Support)
2 Center Midfield (Support)
2 Wide Midfielders (Attack)
1 Poacher (Attack)
1 Advance Forward (Attack)
It's simple, but it works... It won't work with every one because every team is different.
You just have to do the same. Create a tactic that best suit your squad.