I'm honestly kind of panicking right now because I just spent basically all my savings on a Sony FX30 because I wanted to start a YouTube channel but then my sister asked me to take her graduation portraits and I also have this old a6400 that was my dads but I have no clue what I'm doing when it comes to lenses. I've been using the kit lens that came with the a6400 and everything looks so flat and boring and not like those professional photos with the blurry backgrounds you see on Instagram.

I tried looking it up but there are so many numbers and brands and it's making my head spin like what is the difference between a 35mm and an 85mm and does it change because the sensor is smaller? I keep seeing people talk about a crop factor and I'm worried if I buy a lens it wont even fit both cameras or it'll look weird. My budget is really tight like maybe $300 or $400 at the absolute most because I'm still a student and I need to buy this before her graduation in three weeks here in Chicago.

I need something that makes people look good and gives that blurry background look but I'm so scared of buying the wrong thing and wasting my money. I saw a Sony 50mm 1.8 online for pretty cheap but then someone said the autofocus is loud and bad for the FX30 video? But then there is a Sigma 56mm something? I just want one lens that I can swap between both cameras that will make her portraits look professional even though I'm a total beginner.

• Must work on both the FX30 and the a6400
• Needs to be under $400ish if possible
• Good for portraits (the blurry background thing)
• Easy for a newbie who doesnt understand settings

Is there like one specific lens that everyone agrees is the best for this? I'm so sorry if this is a really dumb question I'm just really overwhelmed with all the technical stuff and I don't want to let my sister down...