you can ride anything between say a 154 and 159. If this is your first board I’d say go with 154 or 155. I’m 5’10 and ride a 156.
dont get anything too stiff. if you’re only 150, you want something somewhat flexible. a stiffer board will kick anyones ass if they’re not heavy enough for it
you also need a wide board with size 12 feet. don’t want toe and heel drag.
as far as gear, you’re probably a medium in pants and jacket.