With such pattern (Y/coach only) and low threshold (25k/40k per year) you can barely get close to silver in most star alliance FFPs at best , and you wont go anywhere close to what's important for you.

Most FFPs in star alliance are spending based (ex : few thousand dollars minimum + other requirements) or miles based , so buying cheap Y/coach tickets won't be enough , only full economy , premium economy or business fares are earning something correct

So forget about
.

• redemption rates = don't count much on it unless you can cash lot of miles quickly (eg : credit card) . Otherwise , by the time you will redeem them , there will be a devaluation or two
• lounge access = go with dragonpass or priority pass instead
• upgrades = you need to check in the flyertalk's section of the FFP you want to suscribe , but onboard-upgrades are getting rare nowadays , and paid upgrades (cash and/or miles) depends on lot of factors
• priority check-in = only available from gold level

@El Saico = In your case i guess its TAP or maybe take a look at Aegean Miles+Bonus , only if , in the near future you will fly more often (at least >60k/year) and can plan 2 trips to/via Greece

@afterglow = as you live in the USA , I could suggest to also check with united and get the visa credit card associated with mileage plan , this way you can easily collect miles if you spend a lot by credit card and it doesnt affect negatively your credit score