i don’t know if people already know this,
for gathering, mining, and woodcutting u need a tool that have  the same level or more than the resource level. example :

[4]Sage <– means that the plant lvl is 4, and u need at least lvl 4 tool to gather the resources

for u to equip any tool or use any skill related item(ex: recipe book) u need skill level related to at least the the level of that item, this also apply to equipment. example :
‘honey drink recipe’ item level : 3 <– means that your cooking skill need to be at least level 3 to be able to use that recipe

to level  up your skill level  just do the task related to the skill like doing woodcutting to l level up your wood cutting skill

have u ever seen that some item leave locked for buy?

u can unlocked this by doing more quest for that town, i think it related to your town friendship of that town. and i think some hint about how many friendship need is somewhere at the item description (red in color)

u can view your town friendship point at quest page, it under the list of each area quest completed