In the long run, your arena is where you will make your most money.
I just did an evaluation of my roster. I believe my roster could be sold off for 3.5 million in cash. I have spent 4.3 million on my arena. I have 0.3 in cash. All in all I am worth close to 8 million. With an unbeaten record in Div 4 while still in the cup and I started in season 20.
So if you want to be rich here are my suggestions:
Invest in your draft (20K per week). You want homegrown players to help build your team in the long-run. I'm not going to sell my 3 draftees until they are 33+ even though they are probably each worth 0.75 million right now.
Build your arena. If you are among the leaders in arena size in your Div you will have more money for a team and have cash left over.
Start getting US players. Once you get to Div IV you will start to see a measurable difference with merchandise. I currently make 15K per week more (35K) than the average in my league (20K).
Start readying a team to win Div 5 title. From the looks of it, you should be getting close to ready.
So to answer your question where to spend money?
1) Draft
2) Players to win title (USA suggested)
3) Arena
For instance I just bought a 32 year old center with a wage of 29K for 100,000. I see you just bought Stokfitz for twice that. To each his own...but it is easier to manage your players with decent salary balance. I'd consider him a 1 year rental to win the title, and then start getting USA players.
With Stokfitz grabbed, I would start looking for salary efficient players you would want to keep more than one season. This will get you a core that will enable you to be competitive in Div 4 while still earning money to build your arena.