Here are the settings:
Initial layer thickness: 0.3mm
Bottom layer speed: 20mm/s
Print speed: 100mm/s
Printing temperature: 215 ©
I am using Ultimaker Original, no heated bed, just acrylic with blue tapes on top. I wiped the surface with isopropyl alcohol before printing, and did the levelling as well.
There are some areas that appear to have too much materials (blobs), and some spots without (or too little) materials. I have attached the photo, filament colour was translucent blue.
Poor adhesion by the sounds of it, printing with the 75C bed. Try your bed at 60c and see if that help. Posting the info that sharky refers to would help a lot.
Sounds to me like some parts of the bed are too close to the nozzle. What happens then is that pressure builds up in the nozzle and as soon as it gets a chance to escape it squeezes out on the sides of the nozzle and creates the blobs you're seeing. This problem usually gets worse with bigger prints (on small prints it might not have time to build up the pressure before going to the next layer). I would start by re-leveling your bed to be slightly further away from the nozzle and see if that helps. Or, you could simply let it continue and it will likely clear up by layer #3 or so.
I fully agree with IRobertI. Re-leveling is certainly a good approach. The extruded material should be adequate to the mean distance between nozzle and bed. You will most probably never get an equally thick first layer on the acryllic bed (at least I didn't). But, as IRobertI mentioned, it will equalise on the following layers.
From your picture I have also the impression that the mean distance between nozzle and bed is a bit too small. If you have an Ulticontroller you might also use the flow option in the Tune menu for reducing the material amount on the first layer and increase it again afterwards. But that more a quick-and-dirty solution...
Or if you want to get even more quick and dirty just grab the z-screw coupler and give it a couple of clicks (twist it) to increase the distance. That's what I used to do when I was lazy and didn't feel like re-leveling 
Or if you want to get even more quick and dirty just grab the z-screw coupler and give it a couple of clicks (twist it) to increase the distance. That's what I used to do when I was lazy and didn't feel like re-leveling
I think this doesn't work with the standard FW, does it? The standard FW blocks the z axis all the time I think...
It works, it doesn't take too much effort to overpower the motor (and for those who are worried, no, that wont harm the motor in any way).
You're all wrong! 
Just kidding. I like IRobertI's explanation the best. You are just a little too close - level farther away. Pressure is building up and when the head passes over a gap in the tape sometimes that releases a blob.
I recommend first layer to be .3mm (default in Cura) that way you only have to level to within about .1mm or maybe .05mm. If your first layer is thinner (say .1mm) then you have to level all that much better (3X in this case or around .015 to .03mm accuracy). A sheet of paper is about .1mm so you have to do a really good job.
You're all wrong!
[...]
We know. But how should we find out before we have written it down...? 
Thank you all for the useful tips! Yes, I didn't see that problem after a few layers.
So the patches where there were no (too little) materials were because the printhead was too close to the bed I guess?
Yes. Too close. No room for all the plastic to come out so it squirts out suddenly when it can.
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yellowshark 152
Can you please provide us with information on your settings for your 1st layer. Bed temp., print speed, layer depth, extruder temp. Are you sing the bed or do you have glass/fibre plate fitted. Did you use anything to improve adhesion - tape, glue, hairspray etc.Were you using a brim, how many lines. Have you been through the bed levelling process?
You are probably suffering poor adhesion. Did the areas where the blobs were show the filament to be raised off the bed?
How well did the filament lay down on the next few layers?
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