So, in order to become part of the active set of 100, an Orchestrator currently needs >1 LPT staked to it.
As for the amount of ETH, this will vary based on gas prices… but here is an estimate:
To register as an Orchestrator, you will need to call 4 transactions:
approve = ~44,009 units of gas
bond = ~627,549 units of gas
transcoder = ~120,548 units of gas
setServiceURI = ~50,957 units of gas
Total = ~843,063 units of gas, which at current gas prices of 34 gwei per unit of gas, would be 0.028664142 ETH.
You can choose to budget for more / less than this, if you would like your registration to happen faster / less fast. Up to you, hope this helps.