shall apply loose powder after foundation, especially the liquid foundation. its used to 'set' the foundation as the liquid one is wet and all.. and also, if you don't apply loose powder after liquid foundation, your face can be quite dirty because dirt can stick on your face quite easily, and also, if you change clothes or anything, can stain the clothes easily.

i dont know what color will suit you... because different brand has different color code. besides, i don't know your exact skin tone.

you have to test the color yourself, and should buy one tone lighter than your skin tone, so then after it oxydize, it'll be like your skin tone or look natural.

hopefully my answer does help.