First of all, I would recommend that you wait a while before deciding that the stretch marks need treatment. Stretch marks are very common after pregnancy and they occur as a result of the combined effects of pregnancy hormones and 'stretching' on the skin. However, stretch marks often mature and fade over time if you just wait a while. For example the dark pink look that stretch marks usually have at first will often fade to a light silvery or white color which may blend into surrounding skin better. If you have dark skin tones, this strategy might not work as well as the colors may not blend together as well.
Most over the counter lotions and balms are just a waste of your money. They are very expensive and most have never been proven to have much effect over just a standard lotion or skin moisturizer.
If after the stretch marks have matured they are still very noticeable, then you will want to start by seeing a dermatologist
. There are several peels and skin treatments that may be helpful and there are also more advanced (and expensive) treatments such as laser based skin resurfacing and dermal microabrasions techniques.