Your first best option is to join guilds, aid everyone, check for any trades that you might want to take in that guild, then leave the guild. This is called guild hopping, and will net you a lot of coins and some very useful blueprints.
Do this over and over for awhile. There is no penalty for leaving a guild other than the wait time to rejoin it. Once you leave a guild, you can't come back for 7 days. Guild hopping for a couple of weeks (or more) might gain you full blueprint sets for a number of great buildings.
While in the guilds, look around. Note if they open level 2-4 of GE. You can't see directly, but if a lot people are asking for levels to be opened on a regular basis, odds are it is a "dead" guild. Few or no trades available when checking the guild box in the Market tab, no recent messages on the main guild tab, or lots of messages where someone is trying to recruit for a different guild are other indicators of a dead guild. There are a lot of them out there, but they are useful for guild hopping.
Read through the main guild thread if you like, get a feel for the various guilds out there. Maybe you'll find one you want to come back to eventually to stay. Good options for a first guild to stay long term in are often guilds that are ranked 25-75 or so with open enrollment enabled. On Mt. Killmore I can recommend Knight's Alliance as one such guild. If you stay in Iron Age, Iron 60 might be a good choice. There are certainly others.