First, ask your doctor which vitamins were low and whether your iron was low or high. “Iron isn’t good” is too vague to choose an appropriate supplement.
If your doctor recommends a general multivitamin, a basic daily product with most nutrients close to 100% of the Daily Value is a reasonable starting point. Expensive bodybuilding formulas and very high doses are not automatically better. The NIH guide to multivitamins explains how to compare labels. Consumer
Confirm whether it should contain iron before buying it. Iron supplements can help when a deficiency is established, but unnecessary iron can be harmful. A multivitamin may also contain too little to treat a confirmed deficiency. The NIH iron guide explains both the benefits and risks. Consumer
Bring the bloodwork to your pharmacist and ask them to match a product to your doctor’s recommendation. Also confirm whether you need a separate supplement, investigation into the cause, and repeat testing. The best choice depends on what is actually low, rather than the brand name