Buying Correct Spare Tubes for 27.5 wheels (and Price Range)

Hi Guys,

Ano po ba ang tamang size ng tube na kelangan ko bilhin? and ano mga considerations na dapat gawin (like sizes and stuff).
I have the Merida 27 2.1 based on the merida website..

also, if you could provide the price ranges para makapili ako (yung budget friendly if possible) hehe..