I do okay with Skarner, but I don't main him. I play him more as super mobile roamer. I try to gank bot after windmill gets capped, . My build is R>W>Q>E. 9/0/21 masteries. arpen reds, as yellows, ms quints, cdr blues. I take flash/exhaust or garrison/exhaust.
Start with boots 5, then build zeal x2. Finish Triforce, then get Phantom Dancer, Frozen Heart. Have ~500 ms with w or speed shrine. After that its situational, I tend to get gunblade or rageblade for some extra punch depending on gold. After that its Frozen Mallet for super easy kiting + hp. If the game is still going, either hexdrinker/FoN vs ap heavy team, Thornmail vs auto attackers, Sunfire vs melee ad.
E is good to poke people on towers, clearing creeps and for procing triforce. R is bread and butter skill, pull people onto your tower, or away from theirs. With frozen heart and cdr runes, w should be up almost always. Spam q constantly when in a fight, the slow from the 2nd q really helps.
I probably have ~15 games played with Skarner