I agree mhsmith0 100%, and let me add this:

The most straightforward path to French victory is to conquer the entire North + Tunis (DEFINITELY in gunboat, but in my opinion that also applies to press). If that is your path to victory, there are only 2 landlocked centers you need to control: Paris and Munich. [url=https://brotherbored.com/diplomacy/gunboat-solo-win-intro/france/]Here's a cheat sheet I wrote for France in gunboat.[/url]

France starts off the match in control of Paris, and Munich is just a stone's throw away from 2 of France's home centers (1 space away from Paris and Marseilles). France will need a few armies to take and hold Munich eventually, but other than that, France's natural targets are far more easy to fight over with fleets. France already starts off with two armies, so only a handful of army builds should be sufficient (and they can be built late in the game).

The main caveat I want to add is that although England and Italy require fleets to conquer, if you really intend to take all the home centers for yourself, you should consider using at least one army. Great Britain is easier to conquer with 1 army convoyed in, and it's really difficult to conquer Italian home centers without at least one army (once Italy is conquered though, a pair of armies in Piedmont and Venice and a pair of fleets at Apulia and Ionian Sea can create a tremendous defense for very little maintenance cost).

France is a much more natural naval than land power, I'd tend to agree with that. Its largest rival, England, is also a naval power, so it MUST have boats to defeat England. It is virtually impossible for France to conquer Germany without getting into North Sea, so there too it must have boats. It is virtually impossible for France to conquer Italy without a couple of ships paving the way. It is utterly impossible for France to conquer Scandinavia without substantial naval power.
etc

The northern part of the board is more heavily dominated by fleets, the southern part more heavily dominated by armies. It's mainly the shape of the board I think.

I happened upon a Diplomacy article discussing French strategy. An interesting tidbit that stuck with me on the build phase: "When in doubt, build a fleet."

The logic behind the advice centered on the idea that sea spaces are larger in size, allowing fleets to move quickly around the board. France also has a Switzerland bottleneck issue, so armies tend to stagnate quickly.

Some Powers are naturally army heavy (for example Austria-Hungary), but I still think the logic holds when doubt creeps in. Every Power, game, and situation is of course unique, but what does WebDip think of the advice overall?