Welcome to the forum....
Oh the joys, everyone will give you a different answer for this one.
For your set up ( and the one I would use of my 10ft #7 rod for sea trout and grilse), for a single fly with the trout size you are targeting, leader should be made up as follows (according to what mono you have), first number being the lighter weight set up and second for a heavier set up: -
Main Fly Line
Five Foot 15-20lb
Four Foot 10-12lb
Three Foot 6-8lb
Hook
Only 2 types of knot needed, 3 turn water knot for nylon to nylon joins and Pitzen or 5 turn tucked half blood from line loop to nylon and nylon to fly.
Tippet diameters in American are quoted as 1x, 2x etc where the diameter is based on the 0x (0.011inches), 1x (0.010''), 2x (0.009'') etc.
Due to the many different materials and mixes lines are made from this has less and less relevance to breaking strain. Best to look for the best bs per diameter.
I use Ultima line as it is cheap but up there with the best.
Ultima Power Match - Maximum Strength Pole & Rig Mono - Ultima UK.
Start with that general set up and then experiment, but don't go less than 6lb with such a heavy outfit as you will get broken as the rod will not adequately protect the tippet from shocks.
It takes me roughly a minute to make up that leader and as the tippet gets shorter as I replace flies, the 6-8lb tippet needs replace roughly every 8 flies. You can also run a dropper of the 10-12lb tail of the joining knot if you so wish.
It will turn over anything from an 8 salmon hook to a size 18 buzzer in the wind and tends not to tangle (poor casting excepted).