Im pretty bad at this game. What's the preferred weapon?
Go to Sheldon's store and test out the weapons he can currently stock for you, choose whatever ones simply suit your fancy. Splattershot Jr. which is what you have from the start is a great starter weapon - it provides a good fire rate at a decent spread and comes with the Bubbler, which is one of the best Specials in the game. Use it when you're in a cinch, or if your partners are going on the offensive, throw it up and share it with them by bumping into your team mates.
What is this about?
The limit left for unlocking Ranked.
Granted, Japan posted this particular tank over 12 hours ago so we've probably reached the cap. It'll probably be available in the morning.