You need to check your voltage with a volt meter and go from there. Solenoids rarely go out but they do. When you are buying new starters and alternators, I assume you mean rebuilt. Unfortunately rebuilt alternators from the parts stores just don't seem to last very long.
#1 Check voltage at battery. Fully charged battery should be 12.6-12.8. If voltage is lower put a battery charger on it over night.
#2 Check all connections. At battery, body ground from engine to firewall, engine ground from - battery to engine.
#3 If everything else checks out, try jumping the solenoid. Make sure vehicle is in park, turn key to run position and take a pair of pliers and jump power from the 2 large studs on the solenoid. From the one going to the battery to the one going to the starter. This will bypass your solenoid. If the starter turns and car starts, you have a bad solenoid or connection from your ignition switch to solenoid. If not it's probably your starter.
Since it starts with a jump I suspect a charging problem. After you get it started after a jump or preferably after charging the battery overnight, check the voltage at the battery. It should be 13.8 - 14.4v. If not you have a charging problem.