We don't necessarily need upgrades, we need to bring the best out of the talent we already have.
Auba, Lacazette, and Ozil can bang goals in for fun but it means nothing if the team concede stupid goals and crumble against the slightest bit of aggression from another team.
Leno is a gamble but they obviously see something that leads them to believe he can be a class keeper with the right coaching, he's still relatively young for a keeper. Torreira is who I'm most excited about, looks like a solid bull of a DM who can also drive forward and play a decent pass or two, something we've not had in over a decade. Someone like him can help get the best out of the likes of Xhaka, Ozil, and Ramsey.
Lichtsteiner brings some much needed competition and can act as a mentor for Bellerin, another who's played nowhere near their potential. He's also an ******** and we need a few of those in our team to get us through difficult periods, he'll hopefully help stop us completely crumbling when things are going against us.
Kos is old and broken, I believe there's a good player somewhere in Mustafi (deeeeeeeeep down) and having someone solid and reliable like Sokratis next to him will help him build some confidence after an awful season. They could be a decent pairing if they click.
We have a lot of players playing nowhere near their potential and I think that's the priority for this window given the limited funds. Bellerin, Mustafi, Mkhitaryan, Ramsey, Özil, Iwobi, Xhaka, Lacazette, and Aubameyang playing at or near their potential can all be amazing players and help push for Top 4. I'm not expecting us to be back in there come the end of the next season, but having a manager and backroom staff that know what they're doing and can spot and bring in talent makes the future seem brighter than it's ever been for Arsenal.