Will 0.5 ml Juvederm give decent results or 1ml for my lips, don't want it to look fake/duck lips. (Photo)

.5 ml would give you subtle improvement, but it will depend on your final results. Lip augmentations with fillers is a great option to improve the fullness, suppleness and symmetry of the lips which can make the mouth appear wider. Results can be very natural-looking and will feel very natural. I prefer to use a micro cannula to inject the lips to prevent bruising. Look for a cosmetic dermatologist or plastic surgeon who is an expert in fillers to discuss your desired results and concerns. 
I hope this helps.

It is always best to have assessment in person to determine the amount, especially for lip filler. Everyone will require different amount base on individually desired look. You can start with 0.5 ml and add more a few weeks after.  

Thanks for sharing your photo and question. It looks as though you are starting with good lip volume and I would careful not to have them overfilled. Start with a smaller amount and add more as needed at followup appointments.