If you have more than 1000 Life Points, this card cannot use its effect, but once "Utopia" runs out Xyz Materials, it cannot use its effect either, so it's better to Summon this card before "Utopia" destroys itself.
"HERO" Decks can effectively use this card to its fullest potential thanks to "A Hero Lives", which halves your Life Points as a cost. After a hit or two (or paying a card like "Warning" or "Judgment"), activating "A Hero Lives" will put you in the LP range required to use the effect of "Utopia Ray". Combined with cards like "Blade Armor Ninja" and "Heroic Champion - Excalibur", this can lead to very quick OTKs.
If you play this card in a "Heraldic Beast" Deck, you can use the effect of this card up to 5 times in one turn. Xyz Summon "Number 39: Utopia", then instantly Xyz Summon this card. If possible, detach all Xyz Materials from this card to increase this card's ATK, then use the effect of "Heraldic Beast Twin-Headed Eagle" in your Graveyard to attach any 2 "Heraldic Beasts" from your Graveyard to this card. Then, detach the remaining Xyz Materials to increase this card's attack from its own effect to up to 5000.
Alternatively, use "Wall of Revealing Light" to instantly make your Life Points 1000. This makes an excellent wall, because then your opponent cannot attack with a monster whose ATK is 7000 or less (which means almost every single monster in the game), and this allows you to more safely prepare for the Xyz Summon this card.
"Hope for Escape" could be useful after reducing your Life Points, but it might be better if you had 2000 Life Points before activating that card.
If you choose to reduce your own life points, remember your opponent can either inflict you Burn damage or destroy "Wall of Revealing Light".
To Xyz Summon this card without using "Number 39: Utopia", you can use 3 copies of "Daybreaker". Special Summon 1 of them with cards such as "Goblindbergh" or "Monster Reborn", then Special Summon 2 more with their own effects, and you now have 3 Level 4 LIGHT monsters ready to be used.
"Shine Knight", "Trident Warrior" and "Level Warrior" are all LIGHT-Attribute. "Level Warrior" can Special Summon itself as Level 4 and "Trident Warrior" can Special Summon "Shine Knight", whose effect turns it into a Level 4 monster.
With 3 Xyz Materials, detach 2 of them for its effect, then "Oni-Gami Combo" to detach the last one. This will allow "Utopia Ray" to attack twice with 3500 ATK.
This combo is even better with a "ZW -" card for extra damage.
Use "Mind Control" to take your opponent's "Number 39: Utopia", then Xyz Summon this card to prevent them from getting their "Utopia" back.
Use "Phantom of Chaos" to remove "Number 39: Utopia" in order to overlay "Utopia Ray" with 1 "Overlay Unit". Follow up with "ZW - Ultimate Shield", to resummon "Utopia" in Defense Position. Then, Summon another copy of "Utopia Ray" in Attack Position. Equip it with "Ultimate Shield".
Since this card's effect requires your Life Points to be 1000 or less and it's ATK and DEF values are the same as "Number 39: Utopia", it is more advantageous to keep "Utopia" on the field instead of directly using it to Summon this card, except if you are in one of the previous situations.
Since this card's effect activates at extremely low LP it's best to have "Megamorph" equipped to double it's attack.
Use this card's effect three times and have it equipped with both "Unicorn Spear", "Phoenix Bow", "Lightning Blade", "Tornado Bringer" and "Leo Arms" for an OTK.
Use "The Winged Dragon of Ra" while you have a high amount of Life Points to immediately make your Life Points 100 so you can use this card's effect AND have another monster on the field with high ATK.
If you need to use the effect of "Utopia Ray" effect, then use "Number 30: Acid Golem of Destruction" and use the negative effect to lower your life points. In order to protect "Utopia Ray"; Xyz Summon a second "Utopia". Make sure you Summon the second "Utopia" before the "Acid Golem". With this strategy you must remember to destroy "Acid Golem" first, since it does prevent you from special Summoning.
When you use this card's effect use all 3 Xyz Material monsters and then attack, but if you use another "Number 39: Utopia" negate the attack, then activate "Double or Nothing" to double the attack point then attacking with an even more powerful "Utopia Ray".