Hi, I'm just new in the 3ds scene and currently playing Pokemon AS with my gf playing Omega Ruby. I'm on my way to Mt. Pyre now and I have some questions.
#1 When is the right time to build the team I want?
#2 Is there something worth getting in Safari?
#3 Is there a missable item/pokemon in ORAS?
#4 Can you explain me in the simplest terms what are EV and IV?
#5 Is the difference between a max EV and good IV big enough compared to a normal one without prioritizing those 2?
#6 How can I know the IV of my pokemon?
#7 Is there a list or tiers of competitive pokemons?
#1 It really depends on what kind of team you're going for, and your personal preferences.
#2
Here, you can find a list of all the Pokemon that can be found in the Safari Zone, to see which ones you'd like to go after.
#3 Don't really know what you mean by that, but if you're talking about a missing item/Pokemon, then all Pokemon including their megas can be used in ORAS, and the only items that are missing are certain Key Items from X and Y.
#4 IVs are individual values, which cannot be changed. They can range from 0-31, and can affect how high a Pokemon's stat can be in a certain stat. For example, a level 100 Alakazam with an IV of 0 in HP will have an HP stat of 220, whereas a level 100 Alakazam with an IV of 31 in HP will have an HP stat of 251. EVs are effort values, which can boosts a Pokemon's stat even further, and are, for lack of a better word, customizable. A Pokemon can have a maximum of 510 total EVs, with a maximum of 255 in a single stat. For example, a level 100 Alakazam with an IV of 31 in HP and no HP EVs will have 251 HP, as I previously stated, but a level 100 Alakazam with an IV of 31 in HP AND 252 EVs in HP will have an HP stat of 314. tl;dr, if you don't plan on playing Pokemon competitively, you don't need to worry about this.
#5 If you're playing in-game, then in most cases, no. But if you're playing competitively, having 252 EVs in Attack can be the difference between a 2 hit knockout and a one hit knockout.
#6 There is an NPC in an area you can't access until you progress through some of the post-game that will evaluate your Pokemon's IVs. The meaning of his quotes can be found
here.
#7 Most people who use tiers in competitive battling follow Smogon's tier system, and a list of their tiers can be found
here. A complete list of Pokemon in each tier can be found
here,
here,
here,
here, and
here.
Hope this helped you out.