Poison Sonata, I'd suggest following the instructions on the Church of Simcountry website (google Church of Simcountry) to get your country in order. Don't worry about building a navy right now - focus on your economy by building corporations, inviting CEOs to build corporations, and investing in infrastructure. Once you're earning a lot of money, build an air force or a navy and use it to conquer a C3.
I'd also suggest joining a federation. If you're a full member or planning to become one, IDC (Independent Defense Coalition) can help and guide you as you work on becoming a top President.
It may be worth it to create a CEO to increase your income. If you do, remember that the best way to make money is to build more corporations.
Lastly, if you ever need any tips on economics, send a message to Money Incorporated or The Republic of Brutillius and I will be happy to help you. Good luck in your investments!
EDIT: In answer to your questions:
- The best fleets use a carrier and navy fighter planes along with cruise ships and ship-based cruise missiles, if I remember rightly. The NFP (navy fighter planes) take out the air force and garrisons of the country whilst the cruise missiles destroy important targets like cities or forts. A good idea would be to add a ground force which you could use to back up your NFP. I know that doing this involves using airdrops and things, but I don't remember how it works. Any vets want to help out here? :P
- White darkness is correct. I, personally, conquered my first country when my profit was at $60B. The best idea is to stay under War Level 3 (you can't be attacked under War Level 3) and only build enough soldiers to take C3s. Once you've taken a C3, dismantle the forces you used to take it so your profit doesn't collapse. A massive mistake many new players make is to have a standing army in countries that can't be attacked. Your main country (your "secured main") can never be attacked, so never have a standing army there. Your other countries can only be attacked once you reach War Level 3, so only build a standing army in those countries once you're ready to move on to War Level 3.
On that note, there is no reason to move to WL 3 unless you are planning on engaging in PvP warfare. I've reached the top 5 on LU without ever getting beyond WL 2 and I probably won't get beyond WL 2 for a while yet. Remember - less military equals more profit.
- Think of the economic disaster right now as being like the recent real-life recession. Some countries (like the US) may be heavily affected, while others (like Australia) might get through nearly unscathed. Ultimately, there's no saying how badly your country will be affected by the recession. All you can really do is ride it out and remember - confidence will save the market. Don't isolate yourself from the world market - keep building corporations as long as you have pop to support them.
Sorry for the lengthy reply :P