Easy money
At the start of your game, be sure that the game speed is not running fast. Now go into the stock market and buy £4 million worth of shares in any of the refineries. When you have bought the shares the price should go up. Sell the shares as soon as this occurs and buy more shares in another refinery. Then, do the same thing yet again. When you have enough money, buy all of the shares you can before May or June in the first year. Then, every three months you should get enough money from the dividends to either build up a lot of money before you build your company or extra cash as you are building your firm.

At times the amount of shares available for the refineries can be really high. If this happens buy as many shares as you can afford. The share price can then go up by thousands. Now sell them right away and keep doing the same thing until your bank balance is what you want.