There aren't many hard rules about the best way to play. Generally you'll want to work on infrastructure as much as possible before your unique advantages (Samurai and Dojo) come into play, and then focus on maximizing those advantages once they're available, ie make a lot of Samurai with the Dojo boost and make good use of them by conquering some cities.
Oftentimes you'll have an AI who's a dick early game and will be aggressive towards other Civs or you, these will often be a good first target, especially if you can get them to declare war on you first and avoid some of the warmonger penalties, or liberate cities/CS they've captured. Especially if you're not planning on winning the game through Domination it's good to try and still remain friendly with some AIs so you can use them for trading and RAs, and also not get dogpiled. Getting another nearby AI to join in a war against someone else is good, though fairly difficult to do in VP, as opposed to Vanilla where it was practically an exploit. Don't completely neglect infrastructure (unless you're playing on Epic/Marathon and want to finish the game in Medieval/Renaissance era), you want to balance war and development of your empire.
Dojo is probably worth getting first so you can get the promotion on as many units as possible, I wouldn't suggest making a huge beeline. Authority is the policy tree to go for, the 20 HP on kill for melee units is amazing for Samurai. Past that, Aesthetics is probably good to push Japan's cultural strength further but I've had decent success with Statecraft, maintaining a decent WC presence is always useful.
If you're unsure about general strategy, watching some youtube playthroughs might help. I'm not particularly huge on him but iirc quil18 is a pretty decent player and does a good amount of VP/CBP.