Don't bother with troops or tanks. You only need those when you're either warring with someone or to deter someone that you've previously attacked.
Tax rate is best at around 35% for bushel prices up to around 48 IIRC... certainly 20% is not being close to optimal.
Pick one strategy and tailor your country to fit that strategy.
As you're a demo the strats you should probably go for are farmer or casher. You could do techer, but tech prices are too low at this point in the game for you to bother.
As a farmer you'll build about 90-95% of your land as farms. The other 10% will be a mix of industrial complexes and construction sites.
As a casher you'll build about 43% of your land as enterprise zones, 37% as residences and the rest, as with farmer, will be a mix of industrial complexes and construction sites.
Go to the Manage link and change production levels to 100% spies.
It is cheaper to specialise your building types and buy the things that you don't produce - ie military, oil and technology (and food if you're a casher).
What will serve you well is to take a glance at other threads in this forum to see more advice on each of the strats. Also, go to the wiki and use
http://www.eestats.com to see the status of all countries playing and market statistics from this, and previous, sets.