For solo top casters Vlad is definitely good. Considerable sustain and poke.

I would probably recommend the following for runes:
Magic penetration marks
Armor seals (since most solo tops are AD based)
Cooldown/AP glyphs
AP quintessences

I play a lot of Kassadin and Lux when I just started, they're both fairly easy champs, Lux's ultimate is very easy to pull off and Kassadin is very easy to run away with using ult. Kass is melee though, and both of them very squishy early game.

If you want someone that can push really hard, go mordekaiser, but he does take some time getting used to.

When looking for a good solo, you're going to look for someone with very good sustain, basically he can heal himself/herself easily while being able to harass the other player and get in a good amount of cs.

For this reason, vlad is very good because of the recent patch, he can sustain very well. Also his pool can save himself from a lot of ganks.

Morg is another choice, while she cant really heal herself as much, has passive spell vamp can heal a great deal every once in a while. Her spell shield is also great against ganks which is why she is another popular choice in mid.

Morde is another good choice, but trickier to use. While he can't really heal, he can make a shield for himself to temporarily absorb damage. This means you can really harass the other laner pretty hard while keeping your hp up.

Lux is insanely powerful if you know how to play her correctly.

Solo top AP caster?

Kennen, Mordekaiser, Vlad, Cho'Gath (Built Tanky Mage Caster or Tank, depending on what is needed on your team plus he's got some great interrupts/cc for team fights)

kassadin owns all

solo top rumble. i won a 2v1 against an annie and malphite. ended the game 12-2-6

also, kennen is a great solo. won 2 ranked games last week playing solo mid.

It all depends on the kind of champion you like to play. The bad thing about most AP carries is that they ALWAYS get focused in teamfights, if the other team has any idea whats going on. That being said, here are some of my favorite AP solo's and why
Brand - If you are good with skillshots, he is BRUTAL. very squishy though
Morgana- More of a support AP than anything, but she can get the kills. Her farming is insane and her stun ability is one of the best IMO.
Fizz - Very easy to play and his ability to escape is insane. If he's fed he can burst down a champ in one rotation of moves

rumble

As solo top, Ryze is only best if you have tear + blue buff. However that qualification means without a coordinated team and a jungler that doesn't need blue, Ryze would be better mid.

I quite like Ken, Vlad and Morde solo top because of the potential sustain. Vlad probably won't win top but is the least likely to lose top if played right.

Morg works more as a strong counter pick against certain top champs.