Um well, this is a good place to introduce yourself but not the best place to look for tips.
Anyway, I'll do my best to answer your questions. First of all you might want to look here if you want to know the locations of certain pokemon: http://www.pokemonreborn.com/forum/index.php?showtopic=6802
Zigzagoon's location should be in there but in case you still can't find it, I'll tell you how. Make sure you have some Pokesnax as sometimes event pokemon won't appear unless you have some. When entering the Obsidia Ward from the Opal Ward, there should be an alleyway on the bottom area near the entrance. Once in there, Zigzagoon will be all the way in the back of the alley.
Ralts also requires you to have pokesnax so that's why it won't go with you. You can find them by buying some from vendors. The closest one in Peridot is in the very top right corner of the area near the entrance to the Jasper Ward.
For levels wise, the best place would be in the Rhodochrine Jungle considering they are the highest level wild encounter's you'll have at the moment.