Self tapes are auditions. Full stop. Period.
You need to treat them as auditions. If you can’t afford to go to a self tape studio (which are very inexpensive, $10-$15) then you need to make sure that your lighting and audio are good. No giant shadows behind your head. No difficulty hearing. I have had a ton of bookings lately from self tapes. They are very common for theatrical co-stars.
If you are going to do self tapes at home, invest in good equipment, decent lighting, a directional or lav mic, a tripod for your phone, and a solid backdrop. You should be able to get everything on the list for less than $100.
Also, failure to turn in self tapes is remembered by both casting and your agent. We get a notification when you upload an ecocast. We can see who didn’t make the deadline. Also ecocast deadlines are firm. After that time, you cannot upload. Be mindful of the time.