Now for your Physic. Jynx isnt a bad choice, but I feel that Alakazam is better. In addition, I think you should maybe try out Bronzor, which will eventually become a Bronzong. Bronzong is the pokemon I used as my physic for my Pokemon Platinum Playthrough. Being a Steel and Physic Type, gives you an advantage against pretty much all pokemon besides either Fire or Ground. Bronzong's ability is either Heatproof (stopping fire moves) or Levitate (stopping ground moves) making you only have to worry about either Fire or Ground, while using Bronzong. If you decide not to use Bronzong, definitely go after Alakazam.
Now for you Leafeon. Leafeon only learns Leaf Blade out of all of those moves, which it learns Leaf Blade at lvl 71, pretty much not allowing you to use that move throughout the entire game. Personally I don't feel like Leafeon is that good, but Besides Roserade and Torrtera, Grass type pokemon fall short.
If you must use a Grass Type pokemon, I prefer Roserade, but otherwise, I think a solid, Ground, Rock/Bug, or Electric type pokemon would replace the grass type, based on your teams.
And if the worst comes to the worst, try out a good Flying type, such as Driftloom,(Ghost/Flying), Togekiss, or Staraptor.
And about the trading, I'm not really sure. But to tell the truth I don't think so. If anything find a friend to help you out. I would help, but I traded in my Platinum.
And last but not least, Dragonite is a great dragon, but I personally prefer Garchomp. Garchomp is a Dragon/Ground Pokemon and could be found early in the game. Since it is Ground/Dragon, it almost has no weaknesses, except against its own type.
I hope I helped
Thank you, it was very helpful. According to my research, Houndoom on Pearl can only be found in routes 214 and 215, and I'm guessing that's not near the beginning of the game? I only have Leaf Green at home, otherwise I'd get it from FireRed or wherever it's found. That's why I thought of Ninetales, because I can find Vulpix easily in LeafGreen.
About the Psychic type, I was thinking Jynx because it's kinda rare AND it's an Ice type pokemon as well. Is it true that Alakazlam has almost the same stats as Kadabra? I think I read that somewhere when doing research yesterday. Oh and is Bronzor found early in the game?
Really disappointed about Leafeon, I really liked it . What about Ludicolo, is it a better substitute?
If not, and the Leaf type isn't an option, do you think I can get a Gastly instead of the leaf type pokemon, and evolve it to Gengar by trading? Can Garchomp learn any electric moves, so that I could have atleast a strong pokemon against flying types.
And I was thinking of getting Dratini from LeafGreen however, I didn't know if you could or could not get it in Pearl.
One other pokemon I like is Scyther/Scizor, I don't know if I could replace anyone from my team though .