I'm also kinda a noob when it comes to firsthand experience with longarms. I've had my .22 rifle for a little over 2 years, scooting in limited range time when I have some spare time and change for a couple boxes of .22.
I know how tempting it is to go out and buy a nice big 308 or similar caliber, but for now find a good .22, a sling, and a bunch of ammo and practice the foundations like sight alignment, stance, breathing, cheek weld, ect. Preferably find someone who's experienced to shoot with that can help correct your skills.
When I first started looking at my first rifle ( no prior shooting experience save for an airsoft M14 that introduced me to the glory of Aperture Sights ) I had 50$ and wasn't getting any money soon. A EddieCoyle, a forum member here very generously gifted me an old JC Higgins .22 . I'm slowly getting better plinking at soda cans and milk jugs Anyway my point is that your "less than 700$" means you have enough money for a mid-upper tier .22 rifle, optics if you desire, a quality sling, and a good amount of ammo with money left over. What you need right now is practice, and you can practice more with a .22 .Once you've handled some more longarms, gotten your
However, if you simply MUST have a centerfire rifle, I understand the desire. Depending on how much you wanna spend, you could get a Mosin Nagant or "Nugget" for 70 bucks and and a crate of 500 rounds of ammo for another 70.