There has been much controversy over whether or not young people should have girl or boyfriends. Some people say a relationship of this kind can bring happiness, others point out that it’s likely to cause troubles. Personally, I do believe that love at an early age is likely to cause troubles. {There are three reasons for this. } --> you can leave out the sentence.
Although the beginning doesn't sound natural, it is straighforward.
That's o.k
Get rid of "in the first, second place.." It is better that we use few linking words. Let your ideas be connected naturally.
In the first place, having a special friend means having more concerns. You have to make great effort(s) to please your partner .{To take an example}--> (don't need this) you have to spend time studying his or her habit in order to meet with what he or she wants. {On the other hand,} --> Instead, it’s better to concentrate on your study and other healthy activities when you are young. You can find an ideal partner later in your life but opportunities to study, obviously, will not be as available.
In the second place, financial problems are worth consideration,(
this is cool! )especially for those who earn just a little or still have to ask their parents for pocket money. {This is due to the fact that many youths would like} To be regarded as being generous, many teenagers are willing to spend all their money on an evening out with their partner to a movie or to an entertainment center. Moreover, gifts on special occasion like birthday or Valentine’s day can make them go through all the money that they have been saving for months.
({Last but not least} --> again unnecessary) Young people are easy to get into emotional problems that they are hardly able to cope with because of inexperience. This appears to be the most serious as it tends to cause great pains and leave youths bitter memories.
{To summarize,} early love can bring young people unnecessary concerns, financial and emotional problems. Therefore, {I do suggest that youths should wait until they are mature enough to get involved in a serious relationship.} --> rewrite this sentence.
Sorry cause I haven't had time to go over sentence by sentence. Your essay is frank and the argument is quite solid. There are several oldfashioned linking words. Before, I used to use them a lot in my essays. I am now trying to get rid of them.