What should i make my 4th Rune page?

Now before i get hate saying that im a bad player, i was wondering. im currently building some general rune pages (AD, AP and tank) and because i bought my 3rd page yesterday, i got double pages so i know have 4 pages. So what do i do with the 4th one? Should i make it crit? (Gangplank, trynd those sorts of people) or what else can i make it? Im a jungler main so a jungle page would be a lot more useful. While im on the topic, what should i do with the Marks (reds) in the ap page? I heard there better at physical damage so i dont want to waste them. Ive been suggested by some friends to get Cooldown reduction marks but im not sure. Also what do i put for my Marks on my tank page? i have had no suggestions on that what so ever. Sincerely, a person who doesnt play much Ranked.