What kind of pump would I need to supply my trailer with water from a nearby creek?
All this is contingent to your property having water rights to that creek. None of it is to be used as drinking water unless you like a good bout of liver flukes, giardiasis, cryptosporidia, hepatitis, typhoid, etc. Not a good idea to contaminate your RV water system with it.

What kind of pump? You start drawing vacuum on top of a 32ft column of water, so the pump will need to be a jet-pump if you plan on pulling water over 28 ft. vertically. Keeping the pump primed is going to be the bane of your existence if the water level in the creek drops below your foot valve. 

A submersible in the creek would get rid of the vacuum issue and the priming issue in one, just don't let it run dry due to sucking your sump empty.

Conversion from head to psi is done by dividing vertical distance by 2.31 so the vertical rise from the pump to your tank system needs to be known. 100 yards on an incline isn't the same thing as vertical rise. Figure rise in ft./2.31 = psi required for the pump to produce to get it to the gravity tank. (how to figure vertical rise below).

Figuring the head needed to give you pressure at the RV requires multiplying psi * 2.31 = rise in ft. so if you want 20psi at the RV, 20psi * 2.31 = 46ft which means your tank needs to be 46ft higher than your RV.

To figure the pressure available at your sprinklers, measure the elevation change from the tank down to the garden, drop in ft./2.31 = psi available to run your sprinklers.

For controls, you need to have a float switch in the gravity tank to keep from overfilling and a way of monitoring for when the creek runs dry to shut the system down so you don't burn the pump out (not mentioned where on the planet you're located).

None of this takes into consideration the amount of wire you need to run down to the pump or the sizing of the wire to reduce voltage loss. It'll have to be 220V to keep the current down, so no 120V pumps. And it will need to be run through a piece of pipe to keep the local wildlife from deciding that Romex is tasty. Squirrels love it.

Any springs or small tributaries uphill from your location? A 1000 gallon stock tank and gravity from there are a lot less energy costly.

Addendum Simple trig for real life or how to figure something you can't measure with two items you can.

You get a protractor, mount it on a stick you can push into the ground, make sure the flat side is level with the angle measurement side down and then sight along from the apex (pencil hole if you're using one of those cheap plastic ones) down to the pump location. Now you measure the distance on the ground from your protractor apex down to the pump in as straight a line as you can possibly achieve following the sight line.

This gives you a right triangle with a known hypotenuse and an angle. You now want to calculate the height of the opposite side. 



If you have Windows, you have a scientific calculator function that can be turned on from one of the dropdown menus. Set the angle function on it to Degrees, enter your angle and click the sine button.



Multiply that by the distance you measured and you should now have the vertical distance between the pump location and a sight line straight out from the RV location. This is the vertical head your pump will have to overcome to get water up to that elevation. As discussed, you will need to place the tank yet further up the hill to have any appreciable pressure at site, so you probably want to measure at that location instead.