My Caviler is possesed

My stupid Caviler sucks! Can someone help me? It only cranks when it wants to. when it doesnt crank it acts like it wants to but just want. I had the fuel pump changed nothing,thensince i had the fuel pump changed and that didnt work i thought i would be safe to change the ignition switch. one day and 305 dollars later still doing the same thing,except now my running lights want come on when its in gear and my backlight on my mileage wants to go out and come back whenever. So I am now out 300 bucks and my car still is acting up, is it the brain,a relay,afuse or what......HELP!!!

Manual or automatic?

Year/ engine?

Check your battery. Use a hygrometer and check each cell for specific gravity (good poor or dead). Not a very expensive tool maybe $10-20 or less. You can also use a load tester $40 or so. Place clamp on posative and clamp on negative terminal of battery and press the load button for 10 seconds or so. This will read out on the meter as good bad or dead etc. If it is not a strong battery place a 2 amp charge on it for the night. Be sure all the cells are full of acid or add water to full line. In the morning after the charge is complete check with tools again. If it is low or dead it's time for a new battery. Hope this helps a bit.