I'm trying to understand what you're talking about from a biblical viewpoint. Where do you see in the bible a reference to a "Feast of First Fruits" and what are the requirements of this feast? Are you referring to this?
Lev 23:10 Speak unto the children of Israel, and say unto them, When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest:
Lev 23:11 And he shall wave the sheaf before the LORD, to be accepted for you: on the morrow after the sabbath the priest shall wave it.
Lev 23:12 And ye shall offer that day when ye wave the sheaf a he lamb without blemish of the first year for a burnt offering unto the LORD.
Lev 23:13 And the meat offering thereof shall be two tenth deals of fine flour mingled with oil, an offering made by fire unto the LORD for a sweet savor: and the drink offering thereof shall be of wine, the fourth part of a hin.
Lev 23:14 And ye shall eat neither bread, nor parched corn, nor green ears, until the selfsame day that ye have brought an offering unto your God: it shall be a statute forever throughout your generations in all your dwellings.
Technically, I don't believe this is a separate feast. It is a ceremony that fell within the feast of unleavened bread.
Let's get this established before we move on, okay?
Lev 23:10 Speak unto the children of Israel, and say unto them, When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest: Lev 23:11 And he shall wave the sheaf before the LORD, to be accepted for you: on the morrow after the sabbath the priest shall wave it. Lev 23:12 And ye shall offer that day when ye wave the sheaf a he lamb without blemish of the first year for a burnt offering unto the LORD. Lev 23:13 And the meat offering thereof shall be two tenth deals of fine flour mingled with oil, an offering made by fire unto the LORD for a sweet savor: and the drink offering thereof shall be of wine, the fourth part of a hin. Lev 23:14 And ye shall eat neither bread, nor parched corn, nor green ears, until the selfsame day that ye have brought an offering unto your God: it shall be a statute forever throughout your generations.
Just as the Crucifixion and the Resurrection are separate events, so Passover and First Fruits are also separate. Can one be kept on its proper day and not the other? Aren't all the feasts important.