Training Items:

Between the fights, when you win, you'll be able to pick three Training Items. What you'll prioritize here are the Power/Speed items. Each Training you'll get a power-only item, a speed item and a balanced item (an item which has power/stamina/speed at once). It'll help you to defeat opponents easily and when you reach the top 10, you'll have practically the Power and Speed gauges at max.

Power Gloves and Speed Boots start to appear later in the game, but these are the best item.

The priority item for each training is:

Power Items:

Power Gloves

Loose Weights Multi Gym (if it appears together with a balanced item) Punch Bag Step-o-Matic

Speed Items:

Speed Boots Track Work Karate Exercycle Speed Bag Jump Rope Jog Machine Running Shoes

Balanced Items (every Training will have one of them at least)

Vitamins Health Club Protein Diet Multi Gym (if it doesn't appear together with a balanced item)