Hi, would recommend that you check with your gynae if the extra vitC is necessary and be careful not to overdose on vitamins as you're already on prenatal vit... (An overdose of vitC could cause digestive problems like diarrhoea and nausea, in worse cases could increase the risks of kidney stones.)
you can take vitamins C just make sure it is stomach friendly . like non acidic vitaminc C. sodium ascorbate will do.
Any brand is fine:) you can decide on the flavour or whether you want chewable/non-chewable/effervescence types
There is probably vitamin c in your multivitamin already
Check with the gyne please