Using the "sandwich method" (moisturizer, then tretinoin, then more moisturizer) can help manage dryness.
Tretinoin 0.1% is the highest standard concentration and can cause significant irritation.
Buying online requires a prescription in many countries, including the USA, UK, and Canada, as it is a potent Retin-A medication. Legitimate Online Sources
Tretinoin (topical route) - Side effects & dosage - Mayo Clinic