Beginners afghan

I’m about to start my first afghan. I wonder if I do it in panels and knit it in a five knit five perl pattern. Would that work out? Should there be a border or can I just start out with that? Thanks for your input.

Do you mean five panels of purling and five panels of knitting? If so, all the panels would look identical as either one of those would result in garter stitch.
If you mean panels knit as 5 knit st, 5 purl st repeated across, it would be fine except that it would result in wide ribbing, looking sort of like the waistband part of a sweater.
If sewing panels together after all that knitting sort of puts you off (I don’t like it!) you could do the whole afghan in one piece working back and forth on a long circular needle. Pick out any stitch you like the looks of, cast on a multiple of the stitches needed, and away you go. As far as a border, you could do a garter stitch border on top, bottom and sides by keeping a certain number of stitches in garter for those areas. Or, use a seed stitch border which is also nice, and also easy.