So i've been workin out for a few fews now, and one major problem has been bugging me!

at my gym, the dumbells go from reallly light ones, to 20/25/30/35/40 and then the massive ones which get all the way up to weights which i cant even begin to imagine.

My issue is that 30s are too light for me , but the 35s are too heavy to do more than 3 or 4 reps.

Should I just keep doing those 3 or 4 reps and try to improve my rep count over the weeks with the 35s (would that work?) or should I keep inceasing my reps with the 30s?

I would stick with the 35 and slowly build your reps. It's hard work and will take a while. Stick with it and things will improve.
Also I would suggest doing some pull ups and some barbell bent over rows with a supinated grip (palms up). Both of these exercises are great and they work the bicep.

Why do you say 30's are too light? How many reps can you do with those?

You can go either way and get progress (lighter/more reps or heavier/less reps.) Either way DB curls aren't going to do a whole lot for your overall progress by themselves though. Add in some heavy compound work like deads and squats, then the choice between 30's or 35's on DB curls won't seem very important. :tucool:

What is your rep range?

Should I just keep doing those 3 or 4 reps and try to improve my rep count over the weeks with the 35s (would that work?) or should I keep inceasing my reps with the 30s?

What is your program? I normally do sets of 25 or 30, so obviously in your position I would go down from the 35. But other people can be doing sets of 3 in which case you might go up from the 35.

I'll tell you one thing that will open your eyes to dumbell curls. Any time you have an in-between weight, you can either get a fractional plate, or you can add dynamic load.

Here is an exercise that will demonstrate this. Stand up and curl the barbells. Now lunge, and as you lunge, uncurl the dumbells. Now recover the lunge and curl the dumbells in a coordinated movement. You might have to do a couple to get the hang of it.

What you should immediately feel, apart from the legs and back involvement, is that the curl is quite a bit harder on your biceps than if you just stand there doing it. The reason is that the distance you raise the dumbells is greater than in the standing curl. If you try this with the 30s that you feel are too light, If you do these smoothly with a reasonable pace, I think you will find out that for this curling exercise, 30s are probably too heavy.

Come on over to my gym...ours go up to 120lbs.
I would recommend working up to 8-12 reps with the 30s.

Work on your rep speed too.

If you are using 30's for example: do slow coutns, 2 second curl, 1 second squeeze, 3 seconds decline.

If you can do 3 sets of 12 honest, non-form-breaking, non-cheating, non-swinging reps of this weight in this fashion, you should really be able to move up to 35's and manage something like:

1x12, 2x8, 3x6 or better next time.

Another option is to follow the same plan, but work until you can get 3X15. Then move on. I used this technique recently to succesfully move my hammer curls up.