That depends. For kit lens.....nah, not necessry. Most likely your lens gonna get filled with dust particle before u notice scratch. Just get a hood if u scare.

However if you plan to go to sandy places, rainy area, or generally lots of small particles, better get a filter so easier to wipe them off. But beware there are good ones and bad so just make sure the filter really is clear. If u notice a faint blur, dont buy.

Btw, some tips to TS. Camera sellers ALWAYS recommend filter to newbie cause they try to earn more money that way and to clear stocks. So dont take everything they said too seriously. But not to say filter has no uses but to protect against UV ray is a BS excuse if they ever mention that.

That depends. Sony 55-210, 50 f1.8 and 35mm f1.8 have same filter thread size of 49mm. So you buy one size fits all. Too bad kit is 40.5mm. But you can buy a 40.5mm to 49mm step up ring.

Then again you might as well buy one for each rather than the hassle of switch all time

Or just no need filter, save hassle and money. Lens dont get scratch that easily. Besides, tiny scartch wont affect img quality.