If you want to reach a high level in table tennis, it's pretty much a given that you need to serve and attack. There are many ways of doing this; it's just a matter of finding ways that match your game. At the higher levels, it's almost all serve and loop, though others serve and hit. You can serve backspin and loop against the likely pushed return, or you can serve topspin and loop or hit the likely countered or topspinned returned.
Should you try to serve and attack with your forehand? Or should you attack with your backhand? That's a question every aspiring player needs to address. And the answer is yes and no.
In general, the forehand attack is more powerful. Therefore, when possible, most players should look to follow their serves up with their forehand. Players who are very fast on their feet and with very good forehands might even force it, running around their backhands to play forehands nearly every time the serve is returned there (at least if it's deep enough to loop). Players who aren't as fast should still look for chances to follow up with the forehand, especially off weak returns off the serve that can be put away.
But even if you can follow the serve up with a forehand, should you do so every time? Probably not. A forehand from the backhand side puts you out of position, and so allows your opponent to block or counter-attack to your wide forehand. You may be fast enough to get to that ball, but it's going to wear you down, and even if you make the shot, it leaves you open on the backhand side. Plus, to cover that wide forehand, you probably have to more immediately after the first forehand, meaning you'll likely be open on your backhand side if the opponent returns the first ball there. The more you attack from the backhand side with your forehand, the more your opponent can get into a rhythm off your attacks, and so he'll get more and more consistent at it.
So rather than become predictable and allowing your opponent to get into a rhythm, mix in some serve and backhand attacks. If your opponent pushes long to your backhand, backhand loop. If you serve topspin and he counters or topspins to your backhand, drive or loop with the backhand. Don't let him get into that rhythm where he knows what you are going to do before you do it. Make him adjust to both forehand and backhand attacks - the shots come out differently, and can cause havoc if you mix them up.
There are advantages to backhand attacks. Besides staying in position, you are facing the opponent as you hit or loop the shot, so you can see what he's doing and where he's positioned right up until the instant you are committed to your own shot. This allows you to more accurately go after his middle (transition between backhand and forehand, usually around the playing elbow), or to switch to a wide angle if you see him out of position. Also, backhand attacks are often quicker and with a shorter stroke, and so will cause timing problems for the opponent, especially if you go back and forth between forehand and backhand attacks. Even the spins are different; most players get more topspin from one side or the other. (A surprising number of players get more spin on their backhand loops than their forehand, causing a lot of balls to be blocked off the end.)
Another consideration is your own serve. If you serve heavy backspin, you are likely to get a heavy push return to the backhand. There's often no huge advantage to looping this with the forehand, so you might as well backhand loop. On the other hand, if you serve with more sidespin or no-spin, and your opponent still pushes it, it's likely to have less backspin and likely pop up a bit. So for those serves you might want to favor the forehand so you can more easily put the ball away.
So develop both a serve and forehand attack and serve and backhand attack. Two guns are better than one.