Also how do you evolve Pokemon who evolve by trading in the main series like Steelix and Scizor?
Requirements
Increasing the recruit rate
In Pokémon Mystery Dungeon: Gates to Infinity, a Gift raises the recruitment rate for Pokémon of one particular type. They are given to the Pokémon and the Pokémon will decide whether to accept the Gift and join the team or not. The Gift isn't lost from the items list after being rejected. These Gifts do not work on evolved Pokémon. There are also Gifts for specific Pokémon. Gifts are given as prizes after completing missions. They can be bought at Cinccino's Gift shop. They are also available with specific passwords.
These are the only ways to increase the recruitment rate in Gates to Infinity, there were a lot more in EoS.
In previous Mystery Dungeon games, Pokemon that evolved via trading in the core series were evolved using an in-game item called the Link Cable. This item is not available in Gates to Infinity however. The thing is though, you don't need it. Here are all the Pokemon that evolve via ''trading'':
Alakazam Machoke Graveler Haunter Poliwhirl Slowpoke Onix Seadra Electabuzz Magmar Porygon Porygon2 Dusclops Clamperl
None of these Pokemon can be found in Gates to Infinity. Case closed.
Source: Bulbapedia
You can also make the leader hold the friend bow to increase the chance of them wanting to join and/or use gifts.
how to evolve Pokemon that require trade
You need to find a link cable to evolve Pokemon that require trading in the older games.
Where to find the item?(in older gens)
>The item itself can be found at the lottery store, the sunken treasure mini game or by taking a treasure chest to Ramparados' hut for P150
Put none of the Pokemon that evolve can be found in gates to infinity and the link cables doesnt even exist in gates to infinity.
Pokemon tha require trade to evolve Alakazam Machoke Graveler Haunter Poliwhirl Slowpoke Onix Seadra Electabuzz Magmar Porygon Porygon2 Dusclops Clamperl Gurdurr Boldore
Hope I helped! :D
Source: exprience and http://www.gamefaqs.com/3ds/683850-pokemon-mystery-dungeon-gates-to-infinity/answers/348560-does-anyone-know-how-to-evolve-pokemon-that-normally-evolve