Nah, brader... ni dia skwat guna dumbbell.
http://www.exrx.net/WeightExercises/Quadriceps/DBSquat.html
Can also try the dumbbell swings and dumbbell snatch.

exrx.net and bodybuilding.com has good guides on how to do the exercises.
Squat guna mesin tu aku tak suka... makes my knees feels weird. It's either I do the leg press, or squat using barbells.

175 cm 48kg... wah you really damn thin leh. And have small frame (and probably weak bones too like me). Your photo looks like me about a year ago (but I'm a lot shorter). =)

I have no idea what are you trying to achieve with the curls and kickbacks. You can curl until the cow comes home. But you aint gonna grow. I did curls for 1 year+. I only became stronger and better in curls. Total berat badan gained = 0.5kg in a year. These are peripheral exercises. For now, you should concentrate on exercises that are closer to the core of the body like various presses, rows, squats and deadlift.

Go read the book Starting Strength by Mark Rippetoe. Pirate it if you have to.

The few programmes I have tried (I think would suit you nicely),
- http://stronglifts.com (go check out it's 5x5 programme, I followed the old version.)
- http://www.defrancostraining.com/articles/...ards-part1.html
- http://simplefit.org 's circuit training. I do this when I can't get hold of any equipment.

You're 16, if you follow a proper programme, eat a lot & sleep well... you're going to have phenomenal growth. You might even grow a lot taller. I envy your age. I would suggest that you increase your overall strength first. Curls and kickbacks can supplement the major lifts later.

And LOMAD (Litre of milk a day), more if you can afford it. It's ridiculously effective. IMO, all weight gainers cost too much, not value for money.

Shah,
I don't know what are you doing lah, and I don't know your strength (I'm assuming you are weak like I was). But if you don't want to waste time, just go do Stronglifts 5x5 or Rippetoe. Don't tangan gatal try to 'customise' the programme by adding this and adding that, yet.

You have no business training the peripheral muscles (arms, forearms, calves) at this stage. All those curl-curl isolation exercise... later when you are stronger. It's like putting big 19 inch tyres onto a Myvi. It ain't gonna take you no where.

Go read everything in Stronglifts.com to gain some basic knowledge first. Get the big muscles strong. Then 3-6 months later, Myvi has become a Ferrari. Now you can put the big wheels, and curl those biceps all day long. =)

And LOMAD.

If you tak cukup equipment at home, can go to those shop lot gym. RM4-5 per entry. I sometimes see school athletes workout at the ghetto gym near my place.

That means you have to pay for his service. And pizzaboy is probably saying that in passing.

Seriously, read up Stronglifts.com first. Pick up some basic knowledge that you can read for free. Then, if you want to employ a PT... go ahead. Why waste money on a PT to tell you simple things? You want to get the pro knowledge from them. =)