This is a simple proof for the first rapture being according to readiness.

Initial Outline
The Tribulation is comprised of 7 trumpets from Rev. 7 to 11, and Rev. 12 to 19 give the details of those major points outlined by the Trumpets. The Seals are the past 20 centuries. The 7th Seal opens up the 7 Trumpets of the Tribulation. The 7 bowls of wrath make up the 7th Trumpet. Rev. 5 is the risen Lord recounting the cross as is the 1st Seal. Rev. 4 is the picture of the universe from heaven. Rev. 2 & 3 is the church age. Rev. 20 is the millennial kingdom. Rev. 21 is after that in the New City and New Earth.

First Rapture Readiness
The first time we see saints in heaven in Revelation is "before the throne" in 3rd heaven in 7.9. This occurs before the first trumpet of the Tribulation is blown (8.7).

So who is taken at that time?

"Then shall two be in the field; the one shall be taken, and the other left" (Matt. 24.40). "Watch therefore: for ye know not what hour your Lord doth come" (v.42).

Who is being spoken to? Believers since it says "your Lord". What are they told to do? "Watch..." So if you don't watch you won't be taken. It's always better to be taken to be with the Lord.

What other passages say the same thing?

"Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man" (Luke 21.36).

What are "these things"? The Tribulation. Where will those stand who watch and pray always? Rev. 7.9 said "before the throne" in 3rd heaven. Whereas those believers alive and left at the 7th trumpet of the Tribulation will "meet the Lord in the air" (not the throne) according to 1 Thess. 4.14-18 since it is according to completion, not according to reward. This "trump of God" (1 Thess. 4.16) is the last trumpet" (1 Cor. 15.52). Saints go to meet the Lord in the air at the start of the 7th trumpet where there "were great voices in heaven" (Rev. 11.15) then at the end of the 7th trumpet Jesus completely "shall descend from heaven" (1 Thess. 4.16), stepping down on the mount of olives (Zech. 14.4, Acts 1.11, Rev. 1.7).

If "thou didst keep the word of my patience, I also will keep thee from the hour of trial, that hour which is to come upon the whole world, to try them that dwell upon the earth" (Rev. 3.10).

If you keep the word of His patience, you will be kept not just from trial and tribulation, but the Tribulation itself - the very hour - that is to come upon the whole world.

God can't make this promise to Christians during the Tribulation, because many of even the most spiritual Christians will be martyred. Death is in no way akin to being kept from the hour of trial. God would prefer you not see death since death is a result of sin as is the second death Hell.