One of the best ways to invest in LEGO is by buying polybags/small LEGO sets...To be precise seasonal/exclusive polybags and sets:
• If you have old polybags from old promotions like Mcdonalds or TRU those would go a lot more than average polybags
• Holiday polybags go more than average one
• They are Halloween, Christmas , May the Fourth , Easter and Summer polybags
• LEGO Brickmaster sets would go for a lot more than average because they were not for sale in stores
• The only thing more than that is some sort of comic/toy con polybags/ sets from the NYC Toy Fair/SDCC
• Polybags might not bring you crazy profits but it can help new LEGO investor invest.
Also, polybags are excellent choices for LEGO investors on a budget. Many double or triple their purchase price months after the set is retired.
Another positive feature of polybags is that they take up very little space to store. Storage is much simpler when investing in smaller polybags. This might help people living in apartments or small houses.