Before we even study any cards ...
Lesson zero is stacks and stack depth. Learn to count everyone's stack in bb, not chips. Always know how many bb you have. Learn what a deep stack, a medium stack and a short stack is. Develop a habit to always pay attention to stacks, whenever the blinds go up (everyone's stack gets shorter!) whenever a large pot moves across the table, and especially whenever action is to you, check your stack depth and everyone else's stack depth that is still in the hand.
Lesson 1 is position. Learn all of the positions, what they are called, and learn the difference between early position (EP), middle position (MP) and late position (LP). Late position - the last 2 seats (CO and BT) we should be playing way more hands - or more accurately, EP and MP we should be playing way less. Learn the difference of being in position or out of position, and the big advantage being in position has.
Most new players' biggest mistake learning is jumping right into playing cards without a clue about stacks or position!
Once we learn stacks and position, THEN we can talk about pre-flop ranges. What cards should open from EP, open from MP, open from LP, what cards should flat defend from EP, flat defend from MP, flat defend from LP, hands that could limp from EP, limp from MP, limp from LP, and hands that could 3-bet from EP, 3-bet from MP and 3-bet from LP. Find charts for these and keep them next to your keyboard or in a popup screen and develop a pre-flop game. When we are new, we can err on the side of tightness (fold some of the weaker hands in these ranges) until we get some confidence. We will also need to know pre-flop bet sizings. Bet sizing might be the trickiest thing in Hold'em, however pre-flop it is fairly simple.
Don't even bother trying to learn fancy post-flop stuff until we get the pre-flop down because the post-flop can be a huge mess and get confusing as all hell if we botch the pre.