necax, English isn't NL's first language either, and you can ALMOST say that about me too.
In just about every case related to advice for an amature player, I am nearly always in the "SPIN IT" camp as your first weapon, unless the ball is too high and dead, then go ahead and power away.
Anyone who has seen my games live, whether lower rated are several levers better than me will KNOW that Der_Echte will spin it up like no other. There is a reason for that, and Next Level and Dan explain it very well. In case anyone missed the advantages of spinning really heavy the first ball given the chance...
1) You get more control of landing percentage
2) You win on your opener or get a ball back to continue attacking with a power shot to win the point or lead to it
3) You surprise your opponent and if he or she does not deal with attacking heavy spin, then they will not attack - big advantage to you
4) You get often the first decisive topspin in the rally
5) You now have a chance to remove spin from your opening shot and win the point, then put heavy spin back on and win
6) You buy yourself more time, ball lands more slowly, gives you more time to see opponent and his shot
7) Timing is more difficult for opponent, much different than the BANG BANG fast topspin they train against
8 - When opponent fast attacks to your FH or pocket, then you can heavy hookshot it, slow it down and bend the laws of physics themselves and land stuff and move opponent out of position to allow you a much easier way to win point on next shot, if they get it back.
I stop at those 8 great reasons.
EDIT: NL highlights the importance of heavy slow spin as it forces an opponent to stop playing by quick twitch instinct and think. Thinking during a point is bad for your TT health, it takes too long.
It also helps to have several BH shots, both heavy spin and speed shots quick off the bounce. Helps, but need so huge if you have a good step around.
Takkyu has been taught all his life to step around and rip the FH, that is Macho TT for Asian players and it is true, and next is quick feet for that. Takkyu has those, but hasn't gotten consistent enough with that fast FH to win the point each time he tries to do that. Spinning every ball like a champ at first is not an easy task either, but it is simple and effective, opens doors for other options if they are trained.
I wanted to keep my first response to what would immediately improve him to ONE area. Dan pretty much simplified it all to (said improve Serve/Receive and Spin/Control game) NL kept it to ONE thing, even though he coulda wrote a whole TT book on that clip.