Do you have any advice for someone who is new to pokemon generation 4 games (Diamond,Pearl,Platinum)?

Try not to get lost by not playing for a while. If you set the game down too long (like a week even), you might forget what's going on. (Thankfully, the first time I played Pearl, I played the game every day for about 3 months. When I finally saw the journal automatically pop up, I was quite surprised!)

Also, try some Dusk Balls at night. If used at night or in caves, they have the same effectiveness as an Ultra Ball and are 200 Poké cheaper.

Dont forget about the split between physical and special attacks. There are now physical attacks for types like water, fire, and psychic. Likewise, special attacks for type like fighting, rock, and flying.

Try lots of different pokemon not just the first ones you get, and don't use a bidoof.

I said stay away from bidoof, not Bibarel.