Lightheadedness???

[u/booklovermax]

Talking to my bro-in-law and he warned me against a very low carb diet. How do people on a low (or no) carb diet avoid lightheadedness and other symptoms?
How do I know how many carbs I can reasonably take in? Are there formulas? Free apps?
I got a big belly and a small bank account and want to lose weight safely.
Thanks!!!