Diversification allows you to recover from the loss of your total investment (20% of your portfolio) by gains of 10% in the two best companies (25% x 40%) and 4% in the remaining two companies (10% x 40%). Even though your overall portfolio value dropped by 6% (20% loss minus 14% gain), it is considerably better than having been invested solely in company E.
The last thing we need to cover before we get into some examples of great beginner stocks is what you should avoid as a beginning investor (and, in some cases, even when you become an experienced investor). Investing in the wrong type of stock can make your portfolio's value look like a roller coaster ride and can even cause you to lose your entire investment.
The reality is that in the modern world - especially with the power of the internet - there is very little information that is not in the public domain somewhere. However, the world now has information overload. Whilst the information might be available, few people now have the time to find or understand it. The people who know these things and can 'join the dots' have regular opportunities for stock market investment.
Dollar-cost average: This sounds complicated, but it’s not. Dollar-cost averaging means investing a set amount of money at regular intervals, such as once per week or month. That set amount buys more shares when the stock price goes down and fewer shares when it rises, but overall, it evens out the average price you pay. Some online brokerage firms let investors set up an automated investing schedule.