phone with more memory and ram and capability of big mini micro sd card

i am in usa and with sprint. my budget is 300$ max

Probably best bang for the Dollar from Sprint would be the Samsung Galaxy S8 Pre-Owned one for $288 but gives the ability to handle up to 256gb Micro SD Card.  A 400gb might work but I have not verified it.
https://www.sprint.com/en/shop/cell-phones/samsung-galaxy-s8-preowned.html?ensembleId=RCCG950UBLK&credit=A2&contractName=0-yr-lb-18months&deviceQuantity=1&plan=pln10970013prd&service=PDSBYUP2&protectionPlan=81400517

The Samsung J7 gives you 400 GB capability, but you lose out on Ram and Internal built in Ram. Same price as the pre-owned S8 $288.
https://www.sprint.com/en/shop/cell-phones/samsung-galaxy-j7-refine.html?ensembleId=SPHJ737PGLD&credit=A2&contractName=0-yr-lb-18months&deviceQuantity=1&plan=pln10970013prd&service=PDSBYUP2&protectionPlan=1100264#tab-overview

Now if you are able to drop another $60, the LG V30 might be one to go with.  Has the 128gb/4g and states that it supports 2TB Micro SD cards.
https://www.sprint.com/en/shop/cell-phones/lg-v30plus.html?ensembleId=LGLS9982BLK&credit=A2&contractName=0-yr-lb-18months&deviceQuantity=1&plan=pln10970013prd&service=PDSBYUP2&protectionPlan=81400517#tab-spec

$300 does not give a lot of options for newer phones.  So as far as supporting the larger Micro SD memory cards might be harder to find on lesser/older phones but that's what I can see/find close to your price range that would get great options for your budget.  You just need to know what you want to sacrifice.

Pretty Extensive list Martin.  Many are well above the $300 price tag and many that do not advertise 400GB Micro SD cards.  

But anyway that is a good list of most of the Sprint Supported phones with a Micro SD Card slot.

Please let us know what your thoughts are so we can help to narrow it down or if there's something else you are looking for.

i do not want to sign any lease or anything with sprint.
just pay 300 buy the best phone and there ends the matter.

lg 30+ if i buy looks like 920$

i do not want 15$ for 18 month type of deal where i can pay remaining balance or upgrade that point(i think i am not eligible to upgrade till then)

can i buy lg 30+ or similar kind of phone out side sprint as unlocked phone for around 360$ and use it?

i like to have 128 gb internal memory phones( any phone with 256 gb memory in my budget) rather than samsung galaxy pre owned 64gb internal memory.
samsung j7 is too less configuration for me

Unfortunately you lock us in a box with the $300-360 price range and 128+ GB Internal memory phones that support over 256GB External (Micro sd) memory.

So here's what I see:
https://www.amazon.com/LG-Electronics-LGUS998U-Factory-Unlocked/dp/B07895W8Z4/ref=cm_cr_arp_d_product_top?ie=UTF8
$399

https://www.bestbuy.com/site/lg-v30-128gb-aurora-black-sprint/6109308.p?skuId=6109308
$397.99 if you activate later from Best Buy.  However $360 if you 'activate today'.
So there's the phone you want at $360.

I feel the Samsung Galax S8 is a much better phone compared to the LG V30+.  If you can overlook the 64gb internal memory and the 12mp camera vs 16mp.  The S8 pretty much beats the V30+.  Better processor better resolution, better front camera,

https://gadgets.ndtv.com/lg-v30-4358-vs-samsung-galaxy-s8-4009

It also appears that the LG V30+ only supports under 200GB External Micro SD card memory.

But as stated, found the LG V30+ at $360.  Let us know your thoughts.

It also appears that the LG V30+ only supports under 200GB External Micro SD card memory.

some one said 2T

i am confused

I stand corrected.  According to LG:
 Supports microSD card
Up to 2 TB (cards sold separately)

https://www.lg.com/us/cell-phones/lg-LS998U-lg-v30-plus

However I still feel the S8 is still a better phone.  But the choice is ultimately yours.

I'll have to agree with all the research that Wakeup has done. With the features you seek and the price range you provide there are not many options, especially if you do not wish to purchase a pre-owned product. The S8 is probably the best bang for the buck, and will probably have the longest support life out of the options available since it was released as a flagship phone last year.

I think the 64GB of internal memory can be offset by the fact you can use a 256GB microSD to expand the memory on the phone, and do back ups as needed of media, which is likely to be the main culprit of phones running low on space.

how my current moto 4g plus different from samsung s8?

If I'm thinking of the correct model, the Moto G4's last Android update is version 7 Nougat, while the S8 will be receiving an update (re-skinned by Samsung of course) of Android 9 Pie.

Spec wise the S8 has a larger, higher resolution screen, and as Wakeup mentioned 64 GB internal storage with an expandable microSD slot that supports 256 GB for sure, 4 GB ram, and higher quality cameras on the front and back.

Any features in particular you are curious about?

It looks like the 4g Plus was released almost a year before the Galaxy S8.  May 2016 vs March 2017.
S8 vs 4g Plus:
Screen size (inches): 5.80 vs 5.50
Resolution: 1440x2960 pixels vs 1080x1920 pixels
Pixels per inch (PPI):  570 vs 401
Processor octa-core: (4x2.35GHz + 4x1.9GHz) vs 1.5GHz octa-core
RAM: 4GB vs 2GB
Internal storage: 64GB vs 16GB
Expandable storage up to (GB): 256 vs 128

Some of the differences are found here:
https://gadgets.ndtv.com/samsung-galaxy-s8-4009-vs-motorola-moto-g4-3501

Just like Martin is asking what features are you concerned about?