Runes and Masteries

So I'd say I have a solid grasp of what's good, but I was hoping to get further insight on how I can optimize my runes. I have 9 pages (purchased a 7 page bundle way back) so I've got pages to work with, and I would like to think my runes are pretty solid. The main page I use is my AP Mid Laner. For mid, I tend to play a lot of poke champions like Xerath, Lux, Ahri, etc. Champions that do plenty of damage that never really get close enough to take damage. I would like to think I'm pretty good at keeping that ideal, typically taking the least damage in the game, even against certain divers, such as Ekko. Because I don't typically take damage, I typically opt for mana regen seals instead of armor or health, so that I can consistently poke without getting too low on mana. In addition, the mana sustain typically allows me to opt for a dark seal and 3 biscuits so that when I get ahead, I can stay ahead. The rest of my runes are pretty straightforward, Magic Pen Marks and AP for the rest. For masteries, I'll typically go with TLD on champions with high burst such as Lux or Ahri, and DFT on champions that I feel have more sustained damage such as Xerath (I've killed many people without bursting them down in short periods) or Karthus (for obvious reasons). When I run 12/18 I almost always go for the magic penetration instead of cooldown reduction unless the champion itself scales mechanically with cdr, such as Orianna, who can constantly reposition the ball with no down time for consistent zoning. Anyway, any tips at all would be appreciated, I'd like to get out of Bronze and maybe into Gold one day.