lol why are you so desperately find black ones,
I am bored with the normal black colour, I would prefer other colour else, to be more special +.+

Actually, there is no so called "supposed time", that's why we've got people who can solve under 10 seconds and people who uses over 1 minute.
It's depend on your own cubing technique, e.g. finger tricks, algorithms you use, cube you use.

Me myself with LBL, 4 look LL, I can get it done in sub-40, and no it's not good, there are people who can sub-30.

And as for the method, the famous one are Fridrich, Petrus and Roux.

Fridrich method is the method used by most of the top cuber, I would say the top 10 in WCA website are all using Fridrich.

Petrus method is said to use the least step to solve. This method is based on block building, and looking ahead is very important in this solve in order to get good time.

Roux method is similar to Petrus but this method needs to inspect 5 pieces at the starting instead of 4 of Petrus and Fridrich. Also, this method uses M slice very often, in which, change of gripping is less often.

There are hell lots of videos available on youtube which you can find finger tricks, tutorial on each methods, even algorithms,
give some patience to watch them.
For the gripping, I can give some idea here.

For right hander, use your left hand to grip,
hold 4 pieces of bottom left corner(reference to F face) with your left thumb,
you middle finger and ring finger on the opposite site,
free up your index finger in order to push U'.

Basically that's the idea, hope you can get it, watch more videos to get a clearer image.

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