Seems like one big problem, I really could use some help!

SO I was soldering the leds I got from ebay today and I did the first cascade (Driver out + to led +, led - to led + for each led then Led- to driver out - closing the cascade). There are 18 of them.
Only the first 3 ones (red) and the last one (blue) light up, and they don't stay lit continuously. They blink on 1-second long intervals. The others don't light up at all.
Any ideas? I'm desperate, really. Am I missing something?What should I look for? Please help!

Tried another driver, same problem, identical. I'm sweating cold here.

First, don't panic .... you'll get it working most likely. You are just learning how to do it first time right?

YOU MUST check every solder joint for continuity and shorts, that is your problem here. do you have a multimeter? if you don't, grab one, a cheap one will do ... are your leds on stars? they are connected in series right?

I have bought a multimeter before, but I have no idea on how to use it. I have it on my lap atm. What am I looking for on each solder joint? I'm afraid the blinking is some kind of safety measure. I can hear a very low "tick" coming from the driver when the 4 lights flicker. So I should turn it on briefly just to test and stop at each 5 seconds or so? I'm trying not to panic but this really pissed me off.
Yeah, first time! And I just discovered I might not be very good with a soldering iron. Mine is 25w, though - is that enough? too much?
I feel dumb for not even having the slightest idea of what's wrong. Everything seemed fine, I didn't take more than 5 seconds to solder each pole, I really don't know.

All the red leds lit up very dimly, all normal except for two that were a little dimmer. (no. 3 and 4)
Blue and white leds didn't light up at all. I'm using the black cable for - and the red cable for +;
Checking the joints now.

When I power the driver on, the last led of the cascade is blue and it lights up "normally" (Flickering like the first three).

Ditto for the joints. No response on the blue or white ones, a slight dimming on the 3rd to the 5th led.

I tried all blue and white ones across my chassis, even the ones I haven't wired yet, and none of them light up... but I'll try again.

One led out of the circuit causes the multimeter to beep; LCD display shows messed up values but stays close to 003, it's a deepred one.

On the cascade I wired, there are 18 leds. All red, except for the last two - Those don't lit at all when tested with the multimeter. But when I turn on the driver, the first three red diodes flicker very brightly, as well as the last one that is blue. And that diode doesn't lit when I test it using the multimeter. =(

There's a low battery indicator on my multimeter's display; this could cause any tests to be pretty innacurate, right?

What's puzzling me is that the last blue diode in the circuit lights up when the driver is connected but doesn't light when tested with the multimeter. Also, no whites or blues light at all when tested. Maybe I need to get a new battery for the multimeter before I continue. I don't want to think that half of my leds are DOA.
Sincerely considering giving up on this one.

What can I take from the fact that the three first red leds light up, just like the last blue one, but none of the others?
Also, what does the blinking mean? Shouldn't they stay continuously lit?

I have to leave for work in an hour or so, will try my best to get a 9v battery on the way, or coming back. I've got a headache already, man, did this piss me off.
Rolling a joint right now, a bitter one. You know? I'm MAD, man. Ahahahahaha. This project's been dragging itself since february or so, and there's always a setback.

• Emitting Colour: Royal Blue445nm /Blue 460-470nm
• DC Forward Voltage: :3.2V ~ 3.6V
• DC Forward Current: 350mA
• Emitting Colour: Deepred 660nm / red 620-630nm
• DC Forward Voltage: :2.5V ~ 2.9V
• DC Forward Current: 350mA
• Emitting Colour: White 5500k-6000k
• DC Forward Voltage: :3.2V ~ 3.6V
• DC Forward Current: 350ma

So, based on this data... Does it make sense that the red diodes were the only ones to light up (very dimly) when tested with a multimeter with a low battery? Since the DC Forward Voltage on blues and whites is higher...?
I could be wrong, I'm still learning.

Btw thanks a lot, Jubiare, you've been really helpful since even before I had a login on these forums.