The best overall game to start with: Dragon Quest XI
Play it on: PC, PS4, Xbox One
Pros
Dragon Quest XI is the most recent mainline Dragon Quest game as of writing (barring any ports or remakes), and coincidentally it’s a near-perfect starting point for the series. While Dragon Quest games often revel in retro sensibilities, Dragon Quest XI features a vibrant 3D world full of modern amenities. There are no random battles, cities are colorful spaces that capture the beauty of Akira Toriyama’s art, and each party member is customizable thanks to the game’s version of skill trees. Dragon Quest XI is a sprawling game with a ton of replay value, so you’ll get a ton of bang for your buck, too.
I could go on about why Dragon Quest XI is a great game, but then Kotaku happens to be the home of probably the most famous Dragon Quest XI review on the English-speaking side of the internet, so you should probably just click here to watch that. From one Tim to another, I approve this message.

Cons
Truthfully, I don’t have a ton of criticism for Dragon Quest XI that doesn’t extend to the series as a whole. I will say that some of the bonus content in Dragon Quest XI S: Definitive Edition does feel like filler and can be tedious. I’d still recommend the Definitive Edition over the vanilla release since it contains some really handy quality of life improvements, but the new stuff doesn’t have quite as much heart as the main game content.

If you like Dragon Quest XI
Dragon Quest VIII is a fan-favorite entry in the series and offers the closest overall experience to Dragon Quest XI. It’s technically a great starting point under normal circumstances too, but unfortunately it’s locked to the PS2, 3DS, and a mobile port that plays pretty rough out-of-the-box. If you have the means to play it, knock yourself out.