All around information to understand the market, mining, exchanges, technical stuff, etc
I recommend you narrow your focus. There are 1000s of alt coins.
Decide which market niche you are interested in then come back and ask the same question. If you are not sure about which market niche you care about then rethink why you are interested in alt coins.
Most alt coins are copy/paste clones destined to fail. Any coin that is successful long term should have a clear focus, be open source and do something both unique and important.
Focusing on "understanding the market, mining, exchanges and technical stuff" is too broad. Even "technical stuff" is not specific. If you really want guidance tell us more about what you are looking for.