First and foremost, practice your last hitting. That is the single most important thing in any lane role in League of Legends.
Pick a champion that seems right for you. Right now, the popular ones are Kassadin, Ahri, Sion, kennen, Ryze, Karthus, Morgana, etc. After you pick your champion and are ready to practice, learn their auto attack animation and get comfortable with it. You can push A then click on a minion to force your character to attack a certain minion the millisecond your champion can autoattack.
As for masteries, I would run 21/9/0 grabbing all the AP/damage you can in the Offensive tree, as well as magic resist in Defense with the extra health. Runes should be Magic Penetration reds/marks, Ability Power per level yellows/seals, and Ability Power per level blues/glyphs with flat AP quints.
Your build usually starts with boots and 3 health potions, as the mobility to farm, evade ganks/harassment, and harass back is super duper important, as well as it enhances your ability to go gank other lanes. And as a tip, always build to win your lane. If you start taking too much damage and keep getting CC'ed by your opponent (or their jungle) and there is nothing you can do, grab merc treads for boots.
The magic resist and CC reduction is well worth giving up extra damage. but I'm going to go my usual build from farming and a normal not incredibly fed game. I usually go 2 Doran's Rings into magic pen boots, into a Deathcap, Void Staff, and then defensive items or more AP damage to either nuke harder or to help keep yourself alive.
If you happen to get super fed, go 3 Doran's Rings, into magic pen boots, Deathcap, Void Staff, into more AP. But these builds are just the normal AP route. Different champs call for different builds.
To put a short version on this:
- Practice your last hitting, this is the most important thing to do in your lane.
- Learn your champions abilities, in and out, as knowing what does what will help you out.
- Watch your minimap and if you feel safe, steal their wraiths to help get yourself ahead. careful though, only do this if you are sure their jungle is nowhere near them, as you do not want to die for the 60 extra gold.
- Did i mention practice last hitting? yes, its this important.
- Watch for your jungler to also give you the blue buff, as unlimited mana is always a good thing for an AP mid.
- Look up a guide. google a guide for a set champion, and build off of that. theres plenty out there that give their advice on what they build for certain champs, what runes, masteries and what skills they level at certain levels.
Those are the things that go through my mind when I solo mid as an AP. I hope its not too confusing and gives good pointers.
The main reason shen takes so little damage in trades is because his W skill, Feint, is a shield. Essentially this adds to his hp every time it comes off cooldown. In order to help damage him, you can make sure to hit him as soon as his shield disappears and is on cooldown. It's a bit tricky, but manageable. Damage dealt when his shield is on is reduced by the strength of his shield.
Another reason you might be dealing less damage than you expect is because of the damage reduction effect of his E skill, shadow dash. Taunted champions deal 50% reduced damage.
Also, Shen gains very high HP regen after hitting a unit he has marked with Vorpal Blade. This lets him regain health lost to harassment much quicker than most other champions.
The final reason you might not be dealing as much damage as you want to is shen's defensive items. If shen is stacking armor, then he is also going to take less physical damage. The solution to this is building armor penetration, such as Last Whisper or Brutalizer, or simply taking more armor penetration from runes.
Best Answer
Gragas is strong cause he has good poke (Q/R), insane burst (if you're good enough to hit everything) and good mobility. Especially in soloq, you can roam all day (after lvl 4 already) and gank sidelanes, cause you have good burst dmg and a pretty strong slow.
Also, his Q has an AS debuff, which is very good late game if you hit the enemy AD/Bruiser, his W gives him dmg reduction and can be up 100% of the time (at rank 5) and it gives him AD, which is very good cause his E scales of AD and AP.
You usually want to skill Q > W >E, cause your E slow/cd doesnt increase/go down, only your dmg increases by a slight amount, so its better to max W second (since W gives you AD, your E dmg increases anyways)
Usually, you get either an Rabadons or an DFG as first item, depending on if the enemy team is tanky and you want to burst one (DFG) or if the enemy team is rather squishy/you want to poke (Rabadons). You usually get 2 Dorans Rings before starting your first core item, and I personally prefer a Chalice of Harmony as well. After you finished Rabadons AND DFG you go for either Void Staff -> Zhonyas -> any AP Item(unholy grail, rylais, abysall etc) or you can build an Abysall after finishing DFG and then go for Rabadons -> Void Staff. Abysall as first/second item is good in a double ap comp and if the enemy has low to 0 MR.
The Problem with Gragas is, that there are very very few real counters to him. In terms of Items, a Banshees Veil does best against him, or on AD champs (even AD carrys!!) consider MoM. You can obviously counter him in lane a bit by picking a ranged champ (Ahri does well, zyra, Morgana) but all these champs can usually only delay his first item a bit, and after lvl4, if he is good, he will start roaming and destroying your sidelanes (Bot!!). Really strong counters mid to him are assassins. Fizz can beat the crap out of Gragas (DODGE AAAALL THE BARRELS!) and so do Talon and even Akali, if played correctly.
Generally speaking, high mobility/MS counters Gragas, cause you can regroup fast enough after his ult or even dodge it. For ADC(which have to be scared to most since Gragas will probably try to burst the AD) you can take Corki/Eze (mobility) or Graves (dash and tankyness). I guess a well played Kog Maw/Caitlyn will also do their job, but its harder.