Hi all!

I have 1 million cash.
I would like to improve my stadium. I have now 1500 seats.

What are your advice, how much seat should I improve my stadium and in what sectors?

Max out VIP seats but don't forget to leave a stand open while you build for your home games.

Good luck and well done for earning the money to get VIPs built so quickly.

Yes.
Build only VIP seats as long as you can build them. After that, build executive seats.

Reason:

VIP and exec give you much more money than regular seats.

I would not buy player before upgrading the stadium. It looks like you don't have a chance to promote to Div IV this season. So you have time to buy players at the end of the season or in the next season.
Better players get more money. So it is important to concentrate at the income first.

Agree with tedX comments - just noticed you are high bidder on an RB with £44k a week wages. If you get him, fire him straight away as this will get you on the road to bankruptcy quickly!

You don't need players of this level to win games in your division. Instead, look for young 3.5* or 4* talent players to improve your squad costing no more than £10k. This will improve your team without hiking up your wage bill too much.