I have Canon EOS 70d DSLR and I have two lenses as Canon 50mm f 1.8 and Sigma 70-300mm. I work with these lenses and it good. Now, I like to add some more lenses like some zoom lens like Canon 18-135mm as its is quite cheap and have seen good reviews on ebay and amazon sites. But I am confused now should I have to buy this lens or not? as I have two lenses which I have mentioned above, Does the needs of canon 18-135mm lens would be fulfill by that lenses or not? As one of the main features that I like to buy this lens is due to image stabilizer feature on it. So can anyone recommend me what should be the best options for buying lens.
It depends on what you are missing with your current lenses.
The 18-135mm is a nice lens that can do a lot but it isn't very good at anything - it's relatively slow at f/3.5-f/5.6, 18mm is wide but not very wide, 135mm is long but not very long, the lens has ok but not great image quality, the auto-focus is ok (much better than the 50 f/1.8) but not great, the IS is ok but not the best, you get the point.
I have the 18-135 and I love it because it does almost everything I need on a daily basis - it covers everything I need to take photos at acceptable parent-child distance in acceptable quality and without swapping lenses.
if you want something that covers everything from sort-of-wide to sort-of-tele with ok quality then the 18-135 is for you. if you want anything more specific (or faster, or higher quality) there are better option out there.