First off, your going to need cash. Hit the voting links daily! Do crimes and thefts till you have some cash saved up. when you do thefts, if you successfully steal a car you can go to your garage and sell it for cash. Once you have some cash saved up go to the stock market. the prices of stocks change every minute. watch the trends to see the highs and lows. Buy stock at a low price, wait a minute or two and wait for the stock to go up and sell for a profit and repeat.
You'll need to refresh the stock market page to see when the prices change. Simply watch the server time clock in the top right corner under communications. Dont forget you can attempt to crack the safe as well giving you nice rewards. Its located at the top of the page as "safe". All these options are timed and you can simply hover over the links at the top to see how much time is left till you can do them again.
OK, now that you have some cash its time to buy a house. you can view the available homes and prices through the homes link on the left under actions. Your home determines your will. The higher the will you have the better results you'll get from working out (better stats). Each home listed has the amount of will you gain below it on the homes page. You'll want to get a home quickly so you can start training. once you have trained and have gotten your stats up a bit you will want to start performing attacks.
Before you attack someone you will need to have bullets. Bullets can be found in the bullet market. Some countries have cheaper bullets than others, all depends on who owns it and what they set the price at. You can also gain bullets and cash from missions. Attacks can be found on the left under the murder section. Be wise when attacking and go for noob accounts to ensure yourself the win. Each win will give you 250exp. That will quickly start to increase your rank. The higher your rank the more energy you will have. Which in turn will give you better workouts (stat increase per workout) and it also increases the maximum amount of stock you can buy at once.
Always pay attention to the leaderboards. it will help you on making decisions on attacks and mugging, etc.
Follow the steps mentioned above and you should find it pretty easy to advance in the game quickly.