As far as I'm concerned, for home use a hydrometer is optional especially if only making small amounts. If it's in your budget go for it. If not, learn to work with it. If you think your syrup is too thin, refrigerate or freeze it. If you bottle it, make sure you are scrupulously clean in everything you do at time of bottling. Under dense syrup is more prone to mold in storage. The syrup going into the jars will be virtually sterile because of long boiling at temps well above 212*F. Any mold spores that enter the syrup will come from contaminated jars, lids and other equipment. Because I too have yet to take the hydrometer plunge I sterilize jars, lids, and my ladle. Also take care not to touch the inside surface of the lids when capping.

Sheeting has worked for me. I have never had a bottle mold in storage and only had one small bottle develop rock candy like crystals a few years ago. I have some bottles left from 2 and 3 years ago that still look as good as they did at the time they were packed. My syrup tastes great and no one ever complains. In fact, they keep asking for more . So just have fun and keep at it