I have hoarding tendencies too, but they've actually been an advantage since we had our second DS.
After DS1 (now 6yo), I didn't throw anything away. I kept all clothes (even down to Tesco bodysuits), steriliser, bottles, bottle insulator things, sippy cups, baby cutlery and plates etc, all toys, books, high chair, portable seat that can be used at the table, sling, seat, baby gym, moses basket, sleeping bags, bedding ... Everything you could imagine.
Then when we had DS2, I barely bought anything as I didn't need to. DS2 did the decent thing, and despite being born three months further into the year than DS1, he was heavier, so all the clothes we had for DS1 are season appropriate for DS2.
Its great! DS2 is now 2yo, and he does have some of his own things, but I don't buy things for the sake of it. The toys etc that we bought for DS1 are exactly the type of things I would buy for DS2 in any case.
We are fortunate enough to be able to afford to buy new things for DS2. But at this age, he hasn't got a clue what was bought for him and what was bought for DS1. But I get that he will get to an age where he is more aware and will have opinions on what he likes. Until then, he will be wearing and using DS1's things!