Of all the little ways you can upgrade your bathroom, this might be the most adult: Get yourself a shower curtain liner that's washable. That's right, you don't have to throw away the liner every single time it gets moldy (think how unnecessarily wasteful—not to mention expensive—that is!). Instead, you'll simply unclip the fabric liner from the rings, toss it in the wash with your dirty sheets, shake it out to dry, and hang it back up again. Shopping for one is not tricky: Just look for the word "fabric," rather than "plastic," in the product name. Then, for all of $13, you'll never have to buy another shower curtain liner again.
In general, getting a fabric shower curtain liner won't run you any more than a plastic one—we're talking polyester here, not silk. It's not so much an aesthetic choice as a less wasteful, more functional one. But if it's your first fabric liner, you will noticet an upgrade in how it hangs (more naturally) and feels (softer!). And washing it really is as easy as tossing it in the wash with a few bath towels to prevent the liner from getting crinkly. If the mildew spots are particularly bad, you can call in reinforcements: Half a cup of baking soda added in with your detergent, followed by half a cup of vinegar for the rinse cycle, will take care of light stains; and half a cup of bleach can go right in with the detergent to take care of a particularly icky mold situation (we get it, sometimes that happens!).
Whatever you do, don't try to wash a plastic shower curtain liner! Get rid of that thing and upgrade ASAP. Note: You can't recycle plastic liners in the traditional sense, but they make great drop cloths for painting projects, and liners to keep your picnic blanket from getting wet.