01 is a remake of the original Rance 1: The Quest for Hikari, but it's still very crude in terms of gameplay, puzzles, plot, writing and humor. It has a good chance of turning someone off the series which would be a shame since it doesn't really represent what makes the later games great. 02 on the other hand wont blow anyone's socks off but at least it's very short, simple, easy and actually is kind of essential for the plot of the rest of the games in the series (with the exception of Sengoku Rance which is mostly standalone).
The order I would recommend is
- Sengoku Rance (which is actually an outlier for many reasons in this series but at least it gives you an idea if you'll love, like or hate these games)
- Rance 02 (it's very short and keep in mind this is a 14 year old remaster of a 33 year old game from 1990)
- Rance III - it has a primitive gui but it's also short. if you truly can't stand playing a game this old, skip directly to Kichikuou Rance
- Rance IV, if you could stomach Rance III
- Kichikuou Rance - The first great game of the series and the one closest to Sengoku Rance in concept (and far grander in plot and direction, but not in gameplay). Could play this first or directly following Sengoku, but it is more meaningful if you've played 02 and III beforehand.
- Rance 5D - 5D is short and interesting, and there's no reason not to play 5D before 6, since the characters introduced in 5D are prominent in 6 and later games.
- Rance 6 - The best story of the series and the second of the four must-play masterpieces of the series
- Rance 01
- Rance Quest
- Rance 9 - Probably the most polarizing game of the series. The gameplay is functional but not exceptional and to many fans disappointing.
- Rance X - The last of the masterpiece games. It's the Endgame of the series, and in a way not even Sengoku Rance can compare to the end of the journey.
As for Sengoku Rance I will say that while yes it's pretty much the clear first game of the series to play-
- It's far more rauchy, horny, lewd and rapey than any other game in the series
- It's plot is kind of mediocre compared to the top games of the series (KR, 6, X and even Rance Quest)
- It actually doesn't have many of the best characters in the series
- In case I forget to say it, Sengoku Rance is brilliant and by far the most brilliant game in the series, even compared to the 3 other masterpieces