i really doubt anyone will trade you those...
but you can get some of those very easily actually. for shaymin get oak's letter (idk where, check bulbapedia.com) and go to the elite four. then go to the white rock. press a. give thanks and than shaymin will appear. follow him. it might be automatic--but i got the game used and he already had shaymin. then there will be a long flowery path. probably use bike, because it is very long. at the end you find shaymin you fight him, catch him he is lvl 30. for darkrai either wait for a nintendo event or get the walk anywhere cheat. if you get walk anywhere go to fullmoon island and walk east til you get to newmoon there is darkrai. also if you have the members card go to the canalave city inn and talk to everyone. one person will take you to newmoon, i think, but you must have members card. members card is only nintendo event though. manaphy you get from importing from Pkmn. Ranger then walk around for egg to hatch. phione...idk. sorry! arceus you must have the azure flute. either action replay or nintendo event. then go to spear pillar. play the azure flute. stairs. go up them. hall of origin, arceus is there. btw he is lvl 80 have a extra master ball from cloning or something or maybe someone very strong. he is normal type though because he has no plate to hold so do not use ghost. hes probably still really strong though. i also heard that when you get the national dex find the man in green at the poke mart and buy the azure flute? but im not sure if thats right. i have Nat. Dex and yet no green man. and thats it!
pkmn. ranger in-game instructions