In my experience, a novice welder should stick to a few basic rod types.
The first two (or three) numbers are the rated tensile strength of the weld material. 60 = 60,000 psi. 70 = 70,000 psi. 110 = 110,000 psi.
6011 - Very forgiving of contamination and technique. Nicknamed "Farmer Rod" for good reason, as it is excellent for repairs of mild steel in tough conditions and akward positons. It is very forgiving to rust and dirt in the base metal, but you should grind out as much of the contamination as possible in order to get the best weld. Once you get the hang of it, the puddle is very controllable. Often used for the first pass under stronger rod. It can be run DC+ or on AC. I use DC+. It leaves a light to moderate cover of slag that sometimes can be difficult to remove.
7018 - Stronger rod that is commonly used to weld low alloy steels. I find it easier to control than 6011, at least in making the weld bead look good. It is known as "Low Hydrogen" rod, meaning it is sensitive to hydrogen embrittlement from moisture contamination. You have to keep the rods in a sealed container, or bake them to drive any absorbed moisture out of the coating before use. It requires the joint to be clean for good results. Grind to clean, bare metal to be assured of a full-strength weld. Normally only used DC+, but you can buy 7018AC rod for use with an AC machine, if AC is all you have. The AC rod is more expensive than the regular version. It leaves a moderate cover of slag that often is easily removed. If the slag is too hard to remove, it is a symptom of a possibly poor weld.
7024 - This rod is good for welding in the horizontal position only. It does poorly in other positions, leading to the nickname "Mud Rod." It has a very rapid deposit rate, and the proper technique is to apply the tip of the rod to the joint letting the arc consume the rod, rather than moving the rod along the joint. It makes a pretty weld if done right, very similar to innershield MIG. It is very easy to use and make a pretty weld, if you can positon your joint to take advantage of it. It leaves a large cover of slag that is easily removed - it often pops off by itself!
These three rods will cover just about anything a non-professional welder might need. 7018 is as easy or easier to use than 6010, and produces a stronger weld. Unless you are doing a lot of welding, the difference in cost of the better rods should not be significant.
Your local welding supply can furnish specific directions for the rod that they sell to you. Most rods will have the industry designation somewhere on the label, sometimes in very small print. Ask the salesman about the designations, appliations, and directions for use.
That Lincoln is a very capable welder within its capacity. I used one to weld 1" mild steel plate, using multiple (many!) passes, and it did a good job. That was 26 years ago, and I just used the bulldozer again this week!
Go to Lincoln's, or Miller's, or Hobart's, or ESAB's websites and look up info about "stick welding". Tons of good info out there.