This is a loaded question.
Despite what anyone might tell you this is a money game. So I've had two objectives every season... either promote or demote (staying in the middle is the worst spot to be) and be training one or more players to sell for a large profit after I move up the ladder with them.
The demotion cycle is to scout and draft a trainee or draft someone to sell if they no longer fit my training program and obviously promotion gets you a nice bonus as you move up. When I'm moving up I typically surround my trainees/core guys with 32-year-old players I find for cheap and can move off of for a small loss in a season or two.
The core of all that money is your arena and I see you're building that up.
The reality is if you want to compete for an NBBA title with these guys that have been playing for all these seasons you'll need $10MM to have a shot at winning and that takes some time to get to. I'm currently sitting at $8.2MM and with how much I make a week my 3rd run at the top MIGHT get started with $10MM after I get to Div IV next season and my trainees can start helping me win and advance.
This is a super high-level musing if you have any more specific strategic questions we can keep this thread rolling or shoot me a BB-Mail.