We present an extragalactic survey using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to characterise galaxy populations up to $z=0.35$: the Valparaiso ALMA Line Emission Survey (VALES). We use ALMA Band-3 CO(1--0) observations to study the molecular gas content in a sample of 67 dusty normal star-forming galaxies selected from the $Herschel$ Astrophysical Terahertz Large Area Survey ($H$-ATLAS). We have spectrally detected 49 galaxies at $>5sigma$ significance and 12 others are seen at low significance in stacked spectra. CO luminosities are in the range of $(0.03-1.31)times10^{10}$ K km s$^{-1}$ pc$^2$, equivalent to $log({rm M_{gas}/M_{odot}}) =8.9-10.9$ assuming an $alpha_{rm CO}$=4.6(K km s$^{-1}$ pc$^{2}$)$^{-1}$, which perfectly complements the parameter space previously explored with local and high-z normal galaxies. We compute the optical to CO size ratio for 21 galaxies resolved by ALMA at $sim 3$.$5$ resolution (6.5 kpc), finding that the molecular gas is on average $sim$ 0.6 times more compact than the stellar component. We obtain a global Schmidt-Kennicutt relation, given by $log [Sigma_{rm SFR}/({rm M_{odot} yr^{-1}kpc^{-2}})]=(1.26 pm 0.02) times log [Sigma_{rm M_{H2}}/({rm M_{odot},pc^{-2}})]-(3.6 pm 0.2)$. We find a significant fraction of galaxies lying at `intermediate efficiencies between a long-standing mode of star-formation activity and a starburst, specially at $rm L_{IR}=10^{11-12} L_{odot}$. Combining our observations with data taken from the literature, we propose that star formation efficiencies can be parameterised by $log [{rm SFR/M_{H2}}]=0.19 times {rm (log {L_{IR}}-11.45)}-8.26-0.41 times arctan[-4.84 (log {rm L_{IR}}-11.45) ]$. Within the redshift range we explore ($z<0.35$), we identify a rapid increase of the gas content as a function of redshift.
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