Fisto, there's no need to stay at the top of your particular league. The essence of the game is mainly to beat down on those lower level than you and get all their resources. This is called "Farming". As you build towards a TH 10 you are just looking for enough resources to upgrade your shit.
The other part is called "pushing trophies". This means trying to get up in the trophy range by winning battles. See when you are farming, you don't necessarily even care if you lose sometimes, as long as you get most or all of the loot, and save your loot from getting stolen.
Going for mainly "wins" starts happening after around 2500 trophies or so, and after 3000 trophies, people are essentially all pretty much maxed out in their upgrades and don't care about resources much at all.
Now the people that you can attack [or that can attack you] only matters on trophies, not on their level, or TH. So a fully upgraded dude could attack a noob if he "dropped trophies" [intentionally losing to get easier opponents]. But there is also the concept of "loot bonus" which is a higher guaranteed bonus after wins in 200 trophy increments. So for a town hall 7, I'd way you are probably fighting at your weight class at 1600 trophies. So go up to 1600 trophies to get into that league, then drop to around the low 1500's so you can still stay in that league, but have to fight easier targets. Only when you go under 1500 trophies will you have to work back up to 1600.
The point to trophy pushing is that at very high trophy levels [after 2400 or so] the bonus gets very lucrative. Also, there are free gems given out at 2000 trophies [500gems], 2600 [1000], etc which allow you to get extra builder huts without paying real money. Also, its more fun to fight at the higher levels.
Also remember to fully upgrade your shit before upgrading your town hall. When you go up in TH, the percentage of loot you can take from the lower levels decreases drastically. Also remember to upgrade your pumps as early as possible since this is beneficial in the long run.
For more info on this "Play Clash of Clans" and "Godson CoC" are good Youtube channels for this.
-Nerd out
PS [I'm currently at TH 9.]