Of course you can wear your girlfriend's (substitute with wife, partner, lover, boyfriend, as required) clothes. You would even satisfy the act of dressing's most basic purpose: to get clothed.
Similarly - on a hunch, dipping into your girlfriend's pots is better than not doing anything at all for your skin (although I cannot prove this theory), but she won't be impressed and she will certainly not thank you for it. Besides, you won't smell right.
Go get your own, because men's skin is different and needs a different level of care. Men's skin has a thicker epidermis (the top layer of your skin), men have thicker facial hair and, crucially, men's skin produces more oil the cause for blocked pores, blackheads and spots.
It is true that knowing your skin type is important in selecting the right care routine. Skin is usually described as normal, oily, dry, sensitive or combination.
If you are reading this, you probably want a quick and easy introduction to skin care. The basic regimen for all types of skin is cleansing, toning, moisturising and that's all I want to introduce you to in this skin care guide for men.
Sticking to these three steps will take you a long way towards well-groomed, healthy skin.
If you have very problematic skin, you should consult the expert resources.