Is there a way to import multiple vCards to Gmail contacts manager!

Yes - you need to concatenate all the VCFs in to a single file
...if you're using windows:
# get a command prompt
Windows_Key + R
run: cmd
# change to the directory where all your VCFs are stored
d:
cd   /my_vcfs
# Run this command
copy   /B   *.vcf   all_in_one.vcf

Then just upload the "all_in_one.vcf" file to google and it will grab all your contacts in one go