In top lane, vsing range AP sucks, so what better way to play malphite top, and help out your team in the mid-late game, rather then just constantly feeding. Even if you feed as malphite, his ult is still a very good engage. First you want to go dorans or flask, depending how comfortable you are with your last hitting/trading.

Never trade with your Q level 1, it doesn't do much damage, and also it will drain your mana. Play safe, last hit, and try to farm up. Start to poke around level 3 with Q.

Once you hit level 6. Get angry. You should have at least a flask/doran's, and a catalyst. With these, you should have enough mana/sustain to poke ryze. Poke with Q only. Once low enough you can use your R+E+Q combo, that should = to about 600 dmg. However, if your struggling in lane still , and can't beat him. Use you teleport move, and help out bottom lanes, or prepare for dragons etc. A tp + flash malphite with ult, is very hard to dodge!

During mid game. You want to be with your team (around 15 - 20 mins). Your ult means you can easily dive mid/bot, and get objectives. If ryze split pushes, it's stupid, as he cant do much auto attack damage. Even if you lose a tower, in the long run, a tier 1 - 2 top turret, is not worth compared to a tier 1 - 2 mid turret. Getting mid and dragon objectives is very favorable when you have such a hard engage.

YOu should be able to clear easy with iceborn gauntlet, and your abyssal scepter should make your ult much more devastating.
Split push top ONLY when you have teleport up.

Stick a expansion of previous chapter. Just split top only when you have tp, if not, stay with team, look to find picks/good engage.

Use your hourglass, as you are most likely to be targeted once u finished ur uly