Aromatheraphy in my office AM I overboard and mad

I import this from australia (Melbourne) and it is a good aromatherapy burner . It cost 80 buck . I had another bigger size at home , I place this in my office working table . It is safe and I left it on all the way . But I think the oil to place on it is abit expensive .

I use all these essentials oil . And it cost 61 buck for each bottle and I use half of it within 1 week . I think it is abit costly . Basically what do I do ? I sprinkled on  the vase as I am bathing the vase .
And then I smell 24 hours . I think so I been having wonderful smell for 1 week everyday 10 hour in office . But I think I had to cut down on this . I tried using Bodyshop cheaper home parfum . But I dont know why I find them suxz and funny smells . But these are too costly .

HELP  ME ......