League of Legends (LoL) Question: Who to buy, Trundle or Shaco?

Hi, from my experience I recommend safer then sorry, I think you should buy Trundle and then Shaco or even wait until Shaco will be on free rotation.

If you're experienced with assassins with mana problems and think you have the patience to watch some how-to's before playing shaco, go for him. I've been maining him since s5 and he's the most mentally satisfying champion in game and does a lot of damage when ahead. He's squishy and it's a lot easier to lose a good advantage with though. Build tiamat > greaves > duskblade > i. edge > Titanic hydra > GA > Death's dance/Mercurial Scimitar/Edge of night/Sterak's.

On the other hand, if you feel more comfortable with strong 1v1's, tankyness, and a fighter-type of champion that can front-line and kill really well if ahead, you should go for trundle and go for Bloodrazor + Stalker's > Titanic Hydra > Tank Boots > Gauntlet > Visage > Solari/Righteous Glory/BORK/GA/Thornmail.

Learning the timing on shaco and ganking paths take a lot of time to practice. Trundle, however, isn't any much different than your bruiser types (if i'm not mistaken). If you are looking to increase your champion pool quickly, then Trundle. If you are looking to learn new mechanics and play styles, then Shaco definitely.