Usable Items Limit? Common Usable Items

Is there a limit to how many usable items you can have active at one time? Like for food buffs you can only have 5.

What usable items are common? Right now I'm using

Giga Speed Potion
Vita Plus III
Magiadd III
Penetrating Oil

 

idk if there is a limit, but you can only have 1 type of buff each time
giga speed is support
vita plus is hp
magiadd is mp
penetrating oil is atk
there is element, but idk if its the same as support
(none of those names are official, just what i describe them as)

 

each item classifies as one buff type, even if it has multiple effects. (one item from hanami boosts hp and mp, but only counts as hp buff)
the classes are:
hp up
hp regen
mp up
mp regen
ampr up
aspd up
cspd up
speed up (can be motion speed or movement speed)
hit up (can be accuracy or critical rate/damage)
dodge up (can be flee or evasion recharge)
atk up (can also be weapon atk)
matk up
defense up (can be def/mdef, physical/magic resistance or guard recharge/power)
resistance up (elemental resistance)
element up (damage to element)
vaccine