Hiya
@M_m
Although I try not to get too bogged down with this question, I think it really depends. Some people do convert their very first vacation scheme (I know a few! Not me though, lol), and for others, it takes a second or third go. I've also never seen conversion stats disaggregated to tell you how likely you are to get a TC on your first attempt at a VS. Moreover, if your scheme is at a firm that offer a large number of training contracts, the numbers can be a bit misleading. Even if maybe 60–70% of vac schemers end up getting offers, that figure also includes people who get offers elsewhere and so choose not to accept the offers they might receive at your firm.
Instead of trying to beat the odds by gaming how likely it is you'll convert on the first attempt, I'd say just focus on bringing your best self to the vacation scheme. That is fundamentally all you can do (and often, that’s more than enough). I'm sure
@Jessica Booker would have much more wise things to say, so I'll tag her here too.