I started with the book "Only Astrology Book You'll Ever Need" I did my own natal chart and my spouses with that. From there I actually started studying Jyotish astrology, https://vaultoftheheavens.com/VOTH_ChartCreator/Welcome.aspx, which has some similarities and differences to western astrology.

For good online sources that is tough to say as there are so many out there and it honestly seems like the sites disappear and reappear.

At the end of the day to me astrology is a means to understand myself more, not in absolutes like, I am this way because of my cancer moon, but rather give insights to myself. Like my mars is conjunct with moon in the 6th house so keeping an exercise routine is really beneficial to my body which compared to my own experience of sporadic vs scheduled exercise. As well as the best way to work through my emotions is through a physical activity.