I have all 4 volumes of Conway's all the World's Fighting Ships (1860-1905, 1906-1921, 1922-1946, and the combined 1947-1995 volume) so I can provide quotes on particular ships and nations' naval history if needed...
Well, the first big question is how well can the Poles afford to maintain the ships and what facilities would they need to maintain them? Especially considering that some of the ships they'd get from the Soviets would be in need of serious repair or need their construction completed.
The PoD I was planning for my Polish TL is that Roman Dmowski is found floating dead in the Seine on May 17 1918 instead of Bronisław Piłsudski (probably Bronisław committed suicide in OTL, but the death is a bit of a mystery, here one mysterious death is swapped with another). Bronisław Piłsudski was an anthropologist and brother to Jósef Piłsudski. As his younger brother becomes more important in the struggle for independence going on in Poland, Bronisław is roped into the Polish delegation to the Versailles conference. This exchange of the two men has 3 effects: 1) the delegates to Versailles can talk to Jósef's brother and be reassured that the Poles aren't being led by a flaming socialist, 2) Dmowski being dead means that he isn't writing letters back to Poland telling the NDs to resist the temptation to work with Jósef Piłsudski, resulting in a more united and decisive Polish leadership back home in Poland, 3) Dmowski isn't bad-mouthing Piłsudski at the Versailles conference and isn't aggravating the Brits and the Americans, meaning everyone has a more favourable view of Poland.
(Note that without Dmowski, Paderewski would be the leader of the Polish delegation to Versailles - Bronisław Piłsudski would not be playing a leading role.)
Now, in my TL I wasn't going to have the substitution of Roman with Bronisław radically change the position of the other delegates at Versailles. It was just going to mean that a few close run decisions by the politicians in Poland and the delegates at Versailles took a slightly more favourable path. To end up with our naval Poland, I think we need to assume that the British or the Americans have a change of heart from their OTL wariness about Poland.
Given the interest Britain had in naval matters, we probably want to make it so Britain is the one who adopts a pro-Polish stance in this TL.
So... With a pro-Polish Britain, Poland gets more ships off Germany, probably gets the OTL plebiscite areas in Germany just given to her (the decision to make the Polish claims on Germany plebiscite regions was fairly close run in OTL), Danzig is a Polish port, not an international city. That, combined with the Polish right-wing being more cooperative with Piłsudski means a richer Poland that is more secure in the west and probably less prone to producing stories of atrocities (the Poles weren't actually worse behaved than average in the wars in the east, but they weren't angels and the times they misbehaved did impact how Poland was perceived in the West). So we don't need any extra PoDs to result in Poland doing better in the Polish-Soviet war.
So at the end we have a Poland that has had the stuffing pummelled out of it, but is still much stronger, larger, more secure and more left-wing than OTL's Poland. The bits that matter most in the 1920s are the plebiscite areas Poland gained off Germany and Danzig - so are those enough that Poland can make the hulls it has gained off the Germans and Russians and turn them into a real navy? Not knowing the manpower and facility needs of the ships involved, it's not a question I can answer, so at this point I have to hand over to others.
And even assuming Britain remains friendly after the Polish-Soviet war ends, does Poland have the spare cash to buy some ships off them? Poland basically needs to rebuild itself at this same time, even if we assume that the Soviets don't overrun much of the core Polish areas in TTL's Polish-Soviet war, there's still an enormous amount of damage to be repaired from being a major battlefield in WW1.
And does anyone think that Poland might be able to get some Austro-Hungarian ships? Most would be unsuitable for the Baltic, but even ones designed for southern climes would be be in better condition than the ships they'd get from the Soviets.
fasquardon