I just got into the travel points and miles hobby in the past year, so I have thoughts!
Personally, I focus on cards that give a more flexible currency (via transfer partners) instead of a specific airline or hotel brand. I have a Chase Sapphire Preferred and a CapitalOne Venture. I am able to transfer points from those accounts to many airlines and can use the travel portals to book hotels on points. I was able to book a week long trip to Portugal for 2 with flights, hotels and rental car all covered by points, and I’m not a big spender or a frequent traveler…this was just using a strategy of maximizing sign up bonuses and everyday spending.
Look for offers for sign up bonuses (points awarded after meeting an initial spend). For example, the CSP often runs a bonus of 100k award points after spending $5k in the first 3 months.
If you have more than one card, get to know which have the best bonus categories and spend accordingly (e.g., I use my CSP for all dining out due to the x3 points but my Cap1 for most everyday spending, as all things are x2 points).