Hi Piya,
To prevent ageing multiple options are available like sunscreens, retinoids( retinol creams or
tretinoin),
vitamin c based creams,
Glycolic acid creams, peptides, estrogen based creams,
chemical peels, lasers,
microdermabrasion, Botox and fillers. These can be used alone or in combination as per the skin's requirement. in your case, you may begin with these
Use a good sunscreen daily
Taking vitamin c and antioxidant supplements would be beneficial. Vitamin c helps in
collagen synthesis and antioxidants prevents free radical damage
Use a good moisturiser suitable to your skin type to keep your skin well hydrated.
There is no harm in using tretinoin(
vitamin A derivative). Tretinoin induces collagen production and helps in shedding of dead layers of skin thus helping in reducing fine lines. However it may irritate your skin. Use it in small quantities in night and do not rub it over face. Use of sunscreen in morning is mandatory with retinoids as it makes skin sensitive to sun. Initially in the beginning use it for two hours and as the skin sensitivity decreases you may apply it overnight.
As you are still 29, you may also use a night cream with vitamin A,C,E to prevent ageing. The chances of irritation with such creams would be less as compared to tretinoin.
Hope that answers your query. Take care.