I bought 300 RIV points back in April with some similar thinking - seemed like enough to get a 1 bedroom most of the time, and, particularly while my 2 kids are young, we can probably travel in Jan/Feb when
points charts are low so should get us a good solid week per year. But, I quickly realized I wanted more points and more stays and increasingly began to think about how the future will look as my kids get older. So, I decided to purchase another 300 in July to give me enough points to secure a 2 BR villa during the highest point week of the year - in the meantime, I'm happy to have the extra points to make extra trips. A few thoughts for you.
If, like me, your kids are young, remember that as they get older, it will become increasingly difficult to pull them out of school for a week. I see you're international, so your breaks may be different than here in the US. For us, our spring break is always the week before Easter which, along with Christmas, are the most expensive weeks of the year.
I took a good look at Poly before settling on Riviera. I won't try to sell you on RIV, but I would note a few things about Poly. Aside from September, 300 points is going to limit you to a "resort view" 1 BR at the island tower. I don't know what the ratio of these rooms to other rooms is going to be once the tower is fully declared, but I sense that it is going to be similar to BLT where, you basically need to own at Poly to get the "resort view" rooms. That means they may well book up well in advance of the 7-month mark. And, I'd also note that I've heard a fair amount of complaints about some of the resort view rooms - plenty of people don't care about that, but it is something to think about. If you decide you're going to want the flexibility for preferred or theme park views, you'll need more points.
When buying direct, you can break your purchase up into as many as 4 smaller contracts. I started with 2 150-point contracts and that is what I would recommend. If you buy more, I'd also break them up into smaller contracts for ease of resale should you decide to do that. Also, once you become a DVC owner, you're eligible for member pricing which can be significantly less than new member pricing. This particular incentive period is really good for existing members. There is also some time before Poly sells out, so if you go with 300 now, you will have time to watch future incentive periods and decide when/if you want to add on more points. I think 300 points is a good place to start, particularly since the incentives don't get any better until you go up to 500 points. My second purchase of 300 points ended up being cheaper than my first purchase and, even taking account of two rounds of closing costs, I actually saved money by waiting (that is probably somewhat unusual). And, with Poly, you have the option of looking at resale points to increase your points as well. Unless you were certain you wanted more points right now, I could see going with 300 points to start and giving all of this some time to marinate.
UY - right now, you're thinking Jan/Feb trips, so just about any UY other than Feb/Mar/April are going to be fine. But, as you get into this and decide you might want more trips, think about which months you are LEAST likely to travel to Disney. Ideally, you want those months to come just before the start of your UY. Also, if you think you're ever going to travel in December, I'd avoid a December UY. And, if you tell your guide why you want the UY you want, you'll get it even if they try to steer you toward a different one.
MB is magical beginnings. It is where Disney will pay you $20/point for your current UY worth of points. So, right now, if you were going to get an October UY, you would get 300 points for the UY that began in October of 2024. You can bank them and have double points for the October 2025 UY or you can get a check for $6,000. It is a really nice savings IMO. I took advantage on both of my direct purchases. I don't think there is any limitation on this benefit for international purchasers, but I can't say for certain.
Go to the referral thread and get a referral for $500 off your first direct purchase too.
Hope this is all helpful. Happy to try and answer more questions too.