LONDON -- This article is the latest in a series that aims to help novice investors with the stock market. To enjoy past articles in the series, please visit our full archive.

It's taken a while, but I've finally decided on the last of the ten shares to take its exalted place in the Fool's Beginners' Portfolio. After deciding that an insurer could offer us good prospects while adding a bit of diversity, the choice was between RSA Insurance Group (LSE:RSA) and Aviva (LSE:AV) (NYSE:AV), both of which have slashed their dividends recently and have seen their share prices falling.

The choice is Aviva.

We bought 151 shares at a price at 321.4 pence, which commission and stamp duty took to a total cost of 497.71 pounds.

Here's what the final purchase tally looks like, with all ten portfolio places filled:

CompanyBuy PriceShare CostChargesTotal Cost
Vodafone 168.5p £487.07 £12.44 £499.51
Tesco 305.5p £485.80 £12.43 £498.23
GlaxoSmithKline 1,440.5p £489.77 £12.45 £502.22
Persimmon 617.9p £488.11 £12.44 £500.55
Blinkx 36.94p £487.24 £12.44 £499.68
BP 434.5p £486.58 £12.43 £499.01
Rio Tinto 3,048.4p £487.74 £12.44 £500.18
BAE Systems 332.3p £485.16 £12.43 £497.59
Apple $458.40 £588.48 £17.50 £605.98
Aviva 321.4p £458.28 £12.43 £497.71
Total   £4,944.23 £129.43 £5,100.66

We've invested 100 pounds more than our original target of 5,000 pounds simply because that's what it took to get hold of two Apple shares. I could have reduced the investment in Aviva to compensate, but I really didn't want to drop the final slice as low as 400 pounds.

Why Aviva?
Here are some of the valuation fundamentals of our two insurance candidates:

CompanyPriceHistoric EPSHistoric 
Div, Yield
Forecast EPSForecast
Div. Yield
Forward P/E
RSA 116p 9.5p 5.8% 12.5p 6.3% 9.3
Aviva 321p -15.2p 5.1% 45.7p 6.6% 7.0

On these figures, both look cheap to me, but I think Aviva shareholders have been more shaken by the dividend cut and the shares have been oversold a little more fiercely. But really, I think I'd be happy to hold either of these companies (and I have owned RSA shares in the past, myself).

So the portfolio is now full, and I won't be investing in any new companies unless I choose to sell one of the existing holdings. And I'll only do that if I believe a share has become overvalued or there's a significantly better place for the money. Knowing when to sell is my weakest point, so that will be a challenge for me.

Valuation update
I'll do a valuation update in due course, but I think a quick mention of Vodafone (LSE:VOD) is in order. As I wrote recently, I believe Vodafone is one of those great long-term investments that's ideal for an ISA.

Though it's still early days, Vodafone has already done well for the portfolio. Since I kicked off the series by buying the shares at 168.5 pence apiece in May 2012, we're up 11.7% (excluding dividends) based on the current bid price of 188.3 pence.

Finally, my idea of the kind of shares that should make up the core of a beginner's portfolio is the same as my choice for an ISA, or a retirement portfolio -- or in fact, any portfolio. I'd start with good, strong companies that should stand the test of time and potentially reward you for decades.

Not surprisingly, the Fool's top analysts think similarly, and they have just put together a special report detailing five blue-chip shares that I think would be ideal for anyone at the start of their investing career.

But it will be available for a limited period only, so click here to get your hands on these great ideas that could start you on the road to long-term riches.

Alan does not own any shares mentioned in this article. The Motley Fool has recommended shares in Vodafone. Motley Fool newsletter services have recommended buying shares of Vodafone Group. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.