What do I wish someone told me 20 years ago? Buy a LOT of ammo or reloading supplies and hoard up - especially surplus ammo for rifles like 7.62 x 54mm and .303 Brit. The Greek HXP .303 (reloadable & non-corrosive) I bought 20+ years ago now costs as much for 40 rounds as I bought in "cases" of 480 rounds (ten boxes with 48 rounds/box). Still have some I keep in two WWII bandoleers w/stripper clips for a rainy day. Also have an unopened SPAM can of Czech 7.62 x 54mm . . . also for a rainy day.
40 years ago: Buy up all the $75 British No. 4/Mk 2s you can find, All the $60 Finnish M/39s, and even get a Finnish M/27 or M/28-30 if you can find one. Pay as much as $150. Even more for a cherry M/28-30.
What advice would I give? Practice, practice, practice. And not just from a bench. Shoot in the field under hunting conditions, and practice unsupported offhand and also using a tree for support. Spend at least as much $ on the scope as the rifle. My favorite cost twice what the rifle did. The better you see the better you shoot. Keep records of loads and results. If you reload (and you should) get a chronograph.