The bot requires a minimum amount of funds at all times in order to operate efficiently.
As a rule of thumb, there should be enough funds available for the bot to be able to create at least 100 buy orders on each market (trading pair), at all times. This is the "minimum required funds" for the bot per market for efficient operation.

Note: as markets sometimes tend to go down for extended periods of time, we strongly recommend starting the bot on a market only if you have TWICE the minimum required funds available for it, which will correspond to a funding health of 50%.

The minimum required funds may differ per exchange and even per market. To calculate it, you need to know the minimum order sizes. 

For example, take the Bittrex market USD-BTC. On this market, the bot uses USD to place buy orders to acquire BTC. Bittrex does not tolerate order sizes worth less than 0.0001 BTC. Therefore, to create 100 buy orders, there should always be at least 0.01 BTC worth of USD available (100 times 0.0001 BTC). With BTC at 40000 USD, this would be 400 USD. So 800 USD would be recommended to get started.
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If you are unlucky and your market keeps going down, then you may (not always though) end up with "bags" and,  more importantly, a depleted amount of funds available for placing buy orders. If the bot cannot place enough buy orders, it will start issuing warnings about being underfunded. It will keep working, but likely less efficiently. You will also notice that there will be fewer or no buy orders near the current market price.
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Bittrex trading rules:  https://bittrex.zendesk.com/hc/en-us/articles/360001473863-Bittrex-Trading-Rules
Binance trading rules: https://www.binance.com/en/trade-rule

The rule of thumb only applies when the default aggression of 20% and buy entry modulation of 0% is used.

Higher aggression will increase the funds nearer the current market price. It is this region where there should be enough buy orders. So with higher aggression, you will receive warnings later. We do not recommend aggression levels above the default, better even to set it at 15%.

Higher buy entry modulation will cause the trade engine to acquire funds at a much higher rate. It may therefore very quickly drain your account. We advise to set it at 0% unless you have developed a good feel for the trade engine.
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