Medium time collector answer for you: Thats hard to answer. But you can start a lot of ways. I suggest just taking it really really slow and learning. You will naturally gravitate towards. And I think that no matter what the cost is, or difficulty, its best to find what you like first.
Just browse cards on a website that easily lists out cards visually. I’m partial to https://pkmncards.com/ but anything will do. You can also start in a fun way by choosing a pokemon you think is interesting, but less popular and focus on collecting just those cards of that pokemon. This will also help you get a representative slice of the history of the card game too. For example: Jopo's slime army
Basically anything from the newest sets will always be the most affordable. Anything thats been out a few months usually sees the prices settle down. But the “bulk” cards across the ages are almost always affordable. Its just rarely as glamorous. But there is some pretty art on some inexpensive cards out there.
So yeah! Just enjoy the journey of learning. If there is a topic or idea you have, use the search bar at the top. There is a treasure trove of information here.
Its easy to collect on a budget. Good luck