useful tips one piece?

I decided to see one piece, I don't know in what order to watch the OAVs and the various films .. advice?

for the series watch from first episode, it old but still good

Hello there,
Please allow me to at least try torefrain you from that.

That thing is still on for as long as I can remember. So far, it has about 900 episodes and counting, plus the manga writer claims that it is about halfway and a bit more.
Imagine this:Let's say you do catch up.How would you feel if you have to wait week by week for an unspecified amount of time (probably 20 more years), due to the commitment?
In short:You will drop it most likely,before the even reach the "One Piece"

Moreover, sorry if this is a jab to people that enjoy it, but the plot is really basic and repetitive.Fairytail, HunterXHunter, Naruto etc are all logically lengthy anime that really just provide the same context with a different way.Unless there are other emotional reasons as to why you would want this specifically,I don't see why you would want to pick One Piece instead of any of the basic Shounen Anime.

Lastly,through aaaaall those episodes, it's the same formula.Luffy finds bad guy.Luffy wins bad guy through friendship and plot armor.And it goes on and on and on.
What I am trying to say,basically ,is that the way they make their plot sure may be different from time to time,but it is just some re-heated food. That you get constantly,instead of actual progressive plot.Spin-offs everywhere as well....

I believe I would never be able to finish even 200 episodes of One piece. I think it is most logical to not watch it and choose something else.Heck,I have 500 anime on my watched list,DM me and I will get you anything your taste desires.

That'a all for me.
Ohh and disclaimer:This is my friendly take on the specific subject.Anyone feeling up to go toe-to-toe with me,don't.Because I will just whip out the most used and comfortable argument:iT's mY OpiNioN. And carry on