It's all a matter of personal choice. All I'm going to say is these are the best players at the respective levels;

Lv. 1-30
LF: Tidus / Wakka
RF: Vilucha / Linna / Shaami / Wedge / Eigaar / Blappa
MF: Kiyuri / Svanda / Brother / Berrik / Rin
LD: Ropp / Judda / Lakkam / Doram
RD: Kyou / Zalitz / Naida / Balgerda
GL: Nimrook / Durren / Jumal / Yuma Guado / Miyu

Lv. 31-60
LF: Tidus / Wakka
RF: Vilucha / Argai Ronso / Basik Ronso / Linna / Shaami
MF: Kiyuri / Svanda / Brother / Berrik / Tatts
LD: Ropp
RD: Judda / Irga Ronso / Linna / Naida / Wedge
GL: Nimrook / Yuma Guado

Lv. 61-90
LF: Tidus / Wakka / Nedus
RF: Vilucha / Argai Ronso / Basik Ronso / Linna / Shaami / Larbeight / Isken
MF: Vuroja / Kiyuri / Linna / Mifurey / Svanda / Nav Guado
LD: Ropp
RD: Kulukan / Judda / Irga Ronso / Nav Guado
GL: Nimrook / Nizarut

Lv. 91-99
LF: Tidus / Wakka / Nedus
RF: Vilucha / Larbeight / Isken / Shaami / Linna
MF: Vuroja / Kiyuri / Linna / Mifurey / Svanda / Nav Guado
LD: Ropp
RD: Kulukan / Judda / Irga Ronso / Nav Guado
GL: Nimrook / Wedge