If you are seeing the 'Fee would bring account below minimum reserve' error message while trying to perform a transaction in the LOBSTR wallet, it means that your Lumens (XLM) may be taken up by the network reserve and you may need to top up your Stellar account.
All Stellar accounts must maintain a minimum balance of lumens. The base minimum balance, which is currently 1 XLM, raises by 0.5 XLM with each added trustline, signer or active trade offer. So, if you don't meet the minimum balance requirement, you won't be able to perform outgoing transactions, add trustlines, set up additional signers or create/cancel trade offers.
You can top up your account using debit or credit cards. Just choose the 'Buy Lumens' option in the LOBSTR wallet.
Also, it is possible to purchase XLM through one of the third-party exchange services.
Some of the popular exchanges, which support Stellar (XLM) are:
To transfer more XLM to your wallet you will need to specify your Stellar address, which starts with an uppercase 'G' and can be found on the 'Receive' page.
Memo is not required when sending funds to the LOBSTR wallet, because LOBSTR provides unique addresses for all our users. (If the service that you are using to send a transaction requires you to specify a memo - you can safely enter just 'Lobstr' there).
Please note that LOBSTR does not apply any additional fees, however, there are base Stellar network transaction fees, the amount of which depends on the Stellar network load.
Learn more about Stellar network fees here.