I wouldnt Say Blackbeard is a good starter legend, he would need one unit of every class to Get his captain ability
Best starter Legends are Sengoku, Rayleigh and Cavendish without a doubt
I used to think that too but then I did some thinking on it and realized huh...there's actually a go-to F2P team at the start of the game:
Blackbeard can clear Ivankov easily, who needs zero special ups in order to be useful and pops up like mad every single month as a Raid. A few decent fortnights can quickly get you running something like this:
And from there, one copy of Doffy and a single run of the Buster Call can get you running a pretty strong-hitting team early on:
I'd say starting with Blackbeard is a fairly easy start since you have endless HP and can use random units to get things done, while quickly teaching you how to properly play OPTC as you're forced to learn about classes, orb manipulation, and synergies in order to make the best use of your Legend due to a lack of dream team. Blackbeard won't hold your hand, but he'll be very, very safe and can do anything Raid Mihawk can do when you consider that they're both 30% HP cutters who don't have an easy go-to class booster(Mihawk due to a lack of F2P boosters aside from Brownbeard who's only just releasing, Blackbeard due to his teams largely being class-diverse except for the very late game) and rely on orb boosters. The difference is that Blackbeard is way, way safer due to his tank captain status. Plus the best part about Legend Blackbeard is that chances are, if you pull a new unit from Rare Recruit you can immediately think of some use or situation when you'd want to use them with a Blackbeard team. As a proof of concept, I used Gamewith's Sugofest simulator and got this:
Hawkins - Striker sub, weak HP cutter, INT beatstick, defense reducer
SW Zoro - DEX Blackbeard team orb manipulation
Hotori and Kotori - ...orb shuffler? Eh, silvers are silvers
Secret Chopper - Orb manipulation, slightly more annoying to use due to not being a matching class but eh, he can still find space
Crocus - No Mansherry no problem
Diamante - A delayer! A great delayer!
Fukaboshi - Godly, godly unit. A delayer that also boosts himself and both Blackbeards? Yooo
Story Zoro - Eh, sockets are sockets
Timeskip Brook - Slasher unit that delays and boosts himself, potentially more units? Gooood
DEX Kaku - Can't hate on an orb shuffler that's also a Powerhouse unit and a Slasher
QCK Rayleigh - For those moments when you're running four QCK subs, behold! Your orb manipulator
The tl;dr here is that Blackbeard is super safe, perhaps not the easiest but very easy to use early on, and will make your time playing OPTC feel far more rewarding with every new unit you get...also writing this post pretty much settled it for me, if I ever start a new/JP account, I'm rolling Legend Blackbeard as a starting Legend, no question about it.