electrical problem

Hey I'm new to this forum so I'm saying what's up! I have a 98 tacoma 4x4 5 speed reg cab. My electrical problem is that when I first got my truck I tried to put 4 off road lights on the front bumper. Well once I got them all hooked up and working I noticed that when I turn them on my fuel gauge drops to empty and when I turn the lights off it comes back up to full again. I'm guessing that I just don't have enough power and the fuel gauge is the first thing that gives up guessing that I just don't have enough power and the fuel gauge is the first thing that gives up power so the system can power the engine. So I thought adding another battery would solve the problem. This weekend I got another battery , put them together and I still have the same problem. So I was wondering if anyone has had this problem and if anyone has some advice it would be greatly appricated. problem. This weekend I got another battery , put them together and I still have the same problem. So I was wondering if anyone has had this problem and if anyone has some advice it problem. So I was wondering if anyone has had this problem and if anyone has some advice it would be greatly appricated

P.s. my taco is the 2.7L...