Multivitamins are one of the most popular supplements on the market and, I would say, one of the most useful.
I am not generally a great fan of chemical food supplements, unless they are required on medical grounds or as temporary measures. The nutrients we need to live a full and healthy life can be found in the food we (should!) eat. But I understand the value in multivitamins as a backstop supplement, as they do provide the core vitamins and minerals that we may miss on a daily basis, particularly if we live a busy and demanding lifestyle.
In terms of which multivitamins to buy, in general principle the reliable big and supermarket brands all provide the core set of vitamins and minerals required by the body. Some of the more expensive brand options add to this, but if the object is to provide a backstop supplement there is no need to go up the price range to do so.
Also, bear in mind that the body can only process vitamins and minerals to a certain dosage level before discharging what it does not need, essentially in the urine. So, going above 100% of the body's recommended dosage is, on the whole, of little value.