try raising power first by strength traing, maybe trj once or twice so by the time the first game comes around, i might have e or d, or on a good run, c power, and 2 or 3 trj. by the time the 2nd yr game come around after more str traing, and some swinging/batting practice traing to raise my contact to around d or c and power to B. By the time the 2nd yr games are over, i sually have high B or low A power. that gives me enough timeto raise my other stats.

I've done a character with all B's and decent abilities and what I did was:

Strength train and h-recovery for the first year -> everything goes to power.
2nd year: Strength train and practice fielding and gamble to get your other stats to D's and maybe get some abilities.
3rd year: Strength train and practice fielding and gamble to get your stats (other than power) to the C-B range. Then once you're satisfied with that, just do what I did in year one for the remainder of year two.

I believe his abilities was: Clutch 5, Risp 5, Power hitter, Gold glove, Durability and Consistency. Not too great on the abilities side when you compare him to other success mode players with every single ability but compared to the major leaguers in the game, he was definitely up there in terms of stats and abilities combined.

The hardest part of the success mode is getting started. The jump from G-D is way larger than the jump from D-A so as long as you get a good start, you should be able to make characters with almost all B's and maybe one or two C's and some decent abilities.