Been a Mets fan through thick and thin since the 80s. Loved Shea Stadium. Love Citi Field. This place was designed to look like Ebbets Field, obviously. The seats are good from all over with the exception of the occasional obstruction.
Unless you'll be bothered by the left field foul pole, you'll enjoy sitting in 430. It will only be in your line of sight towards parts of the outfield and not at home plate. Even though the outfield fences have been moved in, the outfield is still deep and there are lots of pop ups, all seen very well from these seats. The left field gate is the easiest access point but entering the main gate at the Rotunda is the neatest entrance and is where they usually pass out all of the promotional items and giveaways. The 500s should always be avoided if you can afford to. The club seats stay empty most nights but fill up when the Subway Series begins.
Once you get in, the concourses can be easily navigated and are wide though not as wide as Yankee stadium's.