The next two Mishnayot will talk about the different korbanot (offerings) that are brought on Shavuot. On Shavuot, there are two different types of korbanot that are brought. The first are the Musaf offerings: two bulls, one ram, and seven lambs as olot (burnt offerings). There is also one goat as a korban chatat (sin offering). Afterward, a Mincha (meal offering), which we know as Shtei HaLechem—the two loaves—is brought as well. It is brought with a bull, two rams, seven lambs as olot, and one goat as a chatat. Then there are two other lambs as shelamim (peace offerings). We'll talk about whether these korbanot are allowed to be brought without others.
The Mishnah says: “The bulls, the rams, and the lambs that are brought as Musaf offerings, and those also brought as part of the Shtei HaLechem, are not considered essential for each other.” In other words, if the Musaf bulls are not brought, the bulls for the Shtei HaLechem are allowed to be brought. The same applies to the rams and the lambs. Each group independently has its own internal components that it deals with, and they don't correspond to each other as intersecting groups. Everything that has to be brought with the Musaf offerings and everything that's brought with the Shtei HaLechem are brought as two separate entities.
But internally within each group, let's say the Musaf offering has only five lambs instead of the seven that they usually bring. They would say, “Okay, just bring those five.” But the olot of the Shtei HaLechem have to be brought in their entirety. For example, let's say normally two rams are brought. If the Kohanim (priests) only have one of them, they do not bring. Bring that one ram. The shelamim lambs that are brought with the Shtei HaLechem also have to be brought as a pair. They can't be brought as one animal.
The Mishnah continues: Rabbi Shimon says that if the treasury of the Beit HaMikdash, where the money is stored, does an accounting, and they realize that they have to bring one ram, they can't bring one animal. They may have enough money to offer all of the bulls, the seven bulls needed for the Musaf offering, but they don't have enough money to purchase the nesachim (libations) that go with those bulls. So what do they do in that case? They should even bring one bull together with the proper nesachim, as opposed to offering all the bulls without the nesachim.
What he's basically saying is, in terms of preference, if you have enough money to do one korban correctly, with the nesachim, do one. And then we continue to add to that, but we don't want bulls being brought without the nesachim. That's definitely not how we want it to be done.