From what you state maybe I should try this:
O.S .40 LA . . . . . . . . . . . . . . . . . . . . . . . . . 11X5
GMS2000 .32 . . . . . . . . . . . . . . . . . . . . . . . 10x5
ASP .46 . . . . . . . . . . . . . . . . . . . . . . . . . . . 11X6
Maxnum XL .25 . . . . . . . . . . . . . . . . . . . . . . 10x4
.065 (WASP) . . . . . . . . . . . . . . . . . . . . . . . . 5.7x3
.10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7x4
And I guess I will pick up some of the 9x5, 10x4, 10x5, 11x4 as well. But how will I know what is best? Does the pitch tell me what size is best suited? Or does the flying? I have never flown before so I don't wanna find out the hard way the prop was too small or big. Is there a way for me to determine the correct size before flying?
And for the electric I will try the props I have:
Eflite Park 400 outrunner & Eflite Park 450 outrunner . . . . . . . . . . . 10x7 electric props
AXI Goldline 2826/12 electric for Lanier ST-40 Super Trainer . . . . . 13x10 electric prop
ORIGINAL: buzzard bait
For the OS 40 LA in the Tower Trainer I would use 11x4 or 11x5. I've used both those props on my OS 40 FP, which is about the same as the LA, and they were good for trainers--kept the speed down but gave good climb-out. I've used a 10x5 on smaller faster planes with that engine, but it would also be worth trying on your trainer.
For the GMS 32 on an LT-25 I would try a 10x4 or 10x5. Even an 11x4 might work well. It will fly fine with the 9x6 because it is a very strong engine for that plane, so anything the engine will turn comfortably will work, but more diameter and less pitch will probably be more efficient. Same story with the LT-40 and the .46--anything will fly the plane, but a 12x4 might be good.
You will have slower landings and steeper climb-outs with the larger, lower pitch props. A small, high pitched prop on a big slow plane wastes energy because fuselage drag absorbs a lot of the power.
For the Magnum, I'd try a 10x4 and a 9x5 and see which you like best.
You should get a range of props because you can only guess how they will suit your engine/plane combination in the air. If you get these and do some experimenting you will find what you like:
9x5
10x4
10x5
11x4
11x5
12x4
For the .10, again, it depends on the use. I've run up to 8x4s on .10s, but a 7x4 will work in lots of applications, but so will an 8x3. Spend some money on a bunch of props--they are cheap compared to the rest of the stuff.
Jim