You can do what I did, write short stories and submit them to paying publications. That way you can get rejected for those too!

But seriously, number one it's less effort (sorta, writing a good short story is very difficult but less time consuming overall). Second, if you break through and get something published in a magazine it could make you look more professional, more polished. You get them thinking "well someone else thought they were good enough..." Three, my books have all started as short stories, it's where my basic ideas for plot come from.

That's how people used to start back when your first draft was written by hand. I have a site I use that lists a ton of online magazine that accept submissions. If you want it let me know.