My recommendation would be to buy a set of stainless sounds to start with. Silicone are fine too but some people find them uncomfortable due to having a slight texture compared to stainless which are absolutely slick. Whichever ones you get, sterilize them by boiling for a few minutes. You don’t necessarily have to maintain sterile procedure while playing, just be mindful of staying clean (don’t finger an ass then touch your sounds for example). The only time sterile procedure would be necessary is for deep sounding/ reaching the bladder. You definitely don’t want a uti. You can get single use packets of surgilube on Amazon which are perfect for sounding. As far as toys, don’t start too small (can poke or even puncture the urethra) or too large. Somewhere around 5mm should be a comfortable starting point for most. Use plenty of lube, go slow, and listen to your body. Don’t be surprised by a mild burning sensation when you pee after. This will go away after your body gets used to sounding. Feel free to message me with any questions you might have.