What I can help you with, are some cheats to make your life a lot easier...
How to get some of the Final Aeons:
There's a bridge after the Calm Lands, and before Mt. Gagazet. Go underneath, find the Sunken Cave, pay Yojimbo 250.000 Gil, and he's yours. To get Anima, you'll need all six destruction sphere treasures. Then, go to the Baaj Temple, beat the boss, and go inside the temple. Touch all the stones, and the Chamber of Fayth will open. If you want the Magus Sisters, you are going to have to work for it... Catch all monsters at Mt. Gagazet, go battle in the arena, and you'll get an item. Go to Remien Temple in the Calm Lands, go inside, and fight the summoner. Beat all of her Aeons and then go through the colored door behind her. The Chamber of Fayth will open.
AP Trick:
Capture all monsters on the Tunder Plains. Give each of your players an Overdrive-AP weapon, and fight King Cactuar. Make sure you overdirve modes are set on Stoic. He will hit you, while rising your AP faster then in normal batlle.
Easy Overdrive Trick:
At an inn or shop, go to a help panel. Battle a fiend and try to fill your overdrive gauge. After the battle, your status will be fully restored.
Rikku's Overdrive Mix Table
Click on the link below to get a list of Rikku's Overdrives and which items you have to combine in order to achieve that effect (on the other hand, it will take some time to load, since it's uploaded from my computer, and because it's a big file... Sorry for the inconvinience).
Al Behd Translation
B = P
C = S
D = T
E = I
F = W
G = K
H = N
I = U
K = G
L = C
M = L
N = R
O = Y
P = B
Q = X
R = H
T = D
U = O
V = F
W = Z
X = Q
Y = A
Z = J