Here is the best training spot to help you boost stats in the game.
From Egg (In Training)
Train until rookie in Gym
Spot
Goblimon (lvl 5)
Location : Powerplant #2
Farm Strength until 400 and other stats 300
Goblimon (lvl 8)
Location : Old Cableway
Farm Strength until 500 and other stats 400
Garurumon Black (lvl 7)
Location : Hallowed Hall
Farm Strength until 900 and other stats 800
Psychemon (lvl 20)
Location : StepStep
Farm Strength until 1200 and other stats 1100
Garurumon Black (lvl 21)
Location : StepStep
Farm Strength until 2000 and other stats 1900
Snow Agumon (lvl 36)
Location : Absolute Zero
Farm Strength until 3000 and other stats 2900
Waru Seadramon (lvl 28)
Location : Ship Cabin 2.0
Farm Strength until 4000 and other stats 3900
— Evovle to Champion —
Wargrowlmon (lvl 35)
Location : Control Island
Farm Strength until 4500 and other stats 4400
Weregarurumon Black (lvl 45)
Location : Night Chruch
Farm Strength until 5000 and other stats 4900
Wizardmon / Sorcerormon (lvl 41)
Location : Layer 01
Farm Strength until 6000 and other stats 5900
— Evovle to Ultimate —
Platinum Numemon (lvl 43)
Location : Layer 05
Farm Strength until 7000 and other stats 6900