hard-earned lessons I've learned in videocamera gear for weddings and other *run-and-gun videography.

(not necessarily in order of significance)

1. DSLRs are overrated, esp now that their main advantage, shallow depth of field, is near achieved by videocameras with 1" sensors, and fast lenses. DSLRs  line skip (meaning they have to shoehorn all that captured digital info to fit into (what's really all that's needed) 1920x1080, or just over 2MP(!), don't have autofocus, are heavy and have a form factor suitable for Stills but not convenient  for video. Achieving videocamera ergonomics requires expensive and bulky rigs.

For videocameras:

2. Unless you are getting a Canon C100 or C300, which has the best implementation of AVCHD,  avoid AVCHD! Go with a videocamera that uses the codec XAVC (proprietory to Sony) or the codec used by Samsung (h.265). It must shoot at least 50MB/s, must have IS, ND filters, focus peaking, zebras, and manual exposure control. It should have Picture Profiles. Any camera that has the above will already have audio meters, headphone and microphone jacks.

3. Go 4k now, or at least get a camera that is 4K-ready (read Sony PXW-X70).

4. Buy SD cards  useable to 94MB/s (see #3 above)

5. Built-in XLR inputs are nice but they add $800-900 to the price of the videocamera. An alternative is to get a Beachtek pre-amp for $250.

If you're serious about your craft, you'll eventually get to the point where you'll need the above to fully realize your vision. So skip the multiple purchases (and losing money on resale) and get to where you'll eventually be, right away.
* run-and-gun: a guerilla style of shooting that occurs in hectic, unpredictable shooting situations.