Well if you're going to try a low-dose experiment to ensure that you get back into the swing of things safely, without any bad trips, I would suggest you buy more than an eighth. In fact I'd say buy at least a quarter. Then you can have a nice 1.5 gram trip first, followed by another at 2 grams for similar purposes of reestablishing a sense of ease while in the psychedelic state. I will say though, 1.5 and 2 gram trips are very much entirely worthy on their own terms too, so I recommend not falling into the philosophical trap that the low-dose trips are somehow 'less' than stronger trips in any other way than strength of effects, ie they're not 'less' valuable, they're not 'less' likely to lead to useful realizations, they're not 'less' brave / cool / whatever somebody wants to tell themselves to try to feel like a badass / like a 'real man'. Low-dose shroom trips are great, a few of them have been some of the most rewarding of all of my shroom trips, and ultra-high doses (3 eighths or even a whole half ounce) trips have also yielded lots of 'top ten' shroom experiences. They're totally different subjectively but equal on their own merits in every way but intensity.
Anyway so yeah get more than an eighth I would say, at least 5 grams, so that you can either take 1.5 grams or 1.5 grams follows by 2 grams at a later date for the purposes of getting reacquainted with the powerful, sometimes pushy, often surprising wonders that are psilocybin/psilocin/host of other molecules mushrooms. And then you'll still have enough if you buy at least 5 grams for a whole 3.5 grams to rip the top of your head off (in the best way!) once you have had a few days to relax after your low-dose trip. Otherwise if you just get an eighth you'll have that 1.5 gram low-dose trip and then only have 2 grams more left over, scarcely any stronger than the first, reintroductory trip, and while yes, I did say – emphasize even – that low-dose trips have tons of value and merit in and of themselves, well, so does a high dose trip. Why bother getting reacquainted if you're not going to take it a little further, right? That wouldn't be getting reacquainted before you take the risk of a heavy dose, it would just be tripping on a low dose twice. Great and fine and dandy, but why not go for broke and have both kinds of different experiences, yeah? Pleasure in variety, like.