Looking to start a small collection of specific issues for my 11 year old son (as a future investment for him). I've collected for years, however want to start concentrating on higher $ specific issues. Opinions on which issues are hot right now and will continue to be hot 20-30 years from now? Spiderman 300? Carnage? FF 52? Batman w/ Poison Ivy? Avengers w/ Ultron? Black Panther (a little pricey) , Gambit? Shazam #1? Thor? Obviously some are very high priced and purchasing would take time, but just curious as to thoughts of which to purchase FIRST.

Thanks everyone!