1) "90 mon" --> Plan to get Level 90 for the Elite Four, which will quickly level to 91 during the Elite Four.

  How to get: Clear all trainers except Sevii optionals, Victory Road trainers, and possibly the boat Fisherman.
  Best mons for this: Setup mons, defensively balanced mons, Speed Boost mons, very high power low PP mons (Compoundeyes Shuckle)

2) "93 mon" --> Plan to get a mid-to-high Level 92 for the Elite Four, which will quickly level to 93 during the Elite Four.

  How to get: Clear all trainers except Victory Road Cooltrainers and possibly the boat Fisherman.
  Best mons for this: Balanced mons with no setup move, high power mid PP mons (Drizzle/Drought) with decent Speed

3) "95 mon" --> Plan to get a mid-to-high Level 94 for the Elite Four, which will quickly level to 95 during the Elite Four.

  How to get: Candy at Level 87 or 89 and clear all trainers except possibly 1-3 Victory Road Cooltrainers.
  Best mons for this: High power high PP mons (~80 good PP per segment), especially with high HP/poor typing for E4 Lemonades.

4) "98 mon" --> Plan to get a mid-to-high Level 97 for the Elite Four, which will quickly level to 98 during the Elite Four.

  How to get: Candy 3-4 times (87/89/91/93) and clear all trainers except possibly 1-3 Victory Road Cooltrainers.
  Best mons for this: Very high PP mons (STAB Return/Extrasensory/Wing Attack), mixed attackers, glass cannons with mid-to-low Speed.